In Western Christianity, the Old Testament refers to the books that form the first of the two-part Christian Biblical canon. These works correspond to the Hebrew Bible (Tanakh), with some variations and additions. In the Eastern Orthodox Church the comparable texts are known as the Septuagint, from the original Greek translation of the Hebrew scriptures. The term "Old Testament" itself is credited to Melito of Sardis.
In modern usage, it is sometimes called the First Testament.
Most scholars agree that the Hebrew Bible was composed and compiled between the 12th and the 2nd century BC, before Jesus' birth. Jesus and his disciples referenced it when discussing Jesus's newer teachings, referring to it as "the law of Moses, the prophets, and the psalms ... the scriptures". (Luke 24:44–45) The accounts of Jesus and his disciples are recorded in the New Testament.
The early Christian Church used the Septuagint, the oldest Greek version of the Hebrew Bible, as its religious text until at least the mid-fourth century. Until that time Greek was a major language of the Roman Empire and the language of the Church (except Syrian Orthodoxy which used the Syriac Peshitta and Ethiopian Orthodoxy which used the Geez). Also, the Church Fathers tended to accept Philo's account of the Septuagint's miraculous and inspired origin, and Christ and the Apostles in the New Testament quoted extensively from the text. 
When Jerome undertook the revision of the Old Latin translations of the Septuagint in about 400 AD, he checked the Septuagint against the Hebrew text that was then available. He came to believe that the Hebrew text better testified to Christ than the Septuagint . He broke with church tradition and translated most of the Old Testament of his Vulgate from Hebrew rather than Greek. His choice was severely criticized by Augustine, his contemporary, and others who regarded Jerome as a forger. But with the passage of time, acceptance of Jerome's version gradually increased until it displaced the Old Latin translations of the Septuagint.
The Hebrew text differs in some passages that Christians hold to prophesy Christ, and the Eastern Orthodox Church still prefers to use the Septuagint as the basis for translating the Old Testament into other languages. The Orthodox Church of Constantinople, the Church of Greece and the Cypriot Orthodox Church continue to use it in their liturgy today, untranslated. Many modern critical translations of the Old Testament, while using the Hebrew text as their basis, consult the Septuagint as well as other versions in an attempt to reconstruct the meaning of the Hebrew text whenever the latter is unclear, undeniably corrupt, or ambiguous.
Many of the oldest Biblical verses among the Dead Sea Scrolls, particularly those in Aramaic, correspond more closely with the Septuagint than with the Hebrew text (although the majority of these variations are extremely minor, e.g. grammatical changes, spelling differences or missing words, and do not affect the meaning of sentences and paragraphs).   This confirms the scholarly consensus that the Septuagint represents a separate Hebrew text tradition from that which was later standardized as the Hebrew text (called the Masoretic Text). 
Of the fuller quotations in the New Testament of the Old, nearly one hundred agree with the modern form of the Septuagint and six agree with the Hebrew text. The principal differences concern presumed Biblical prophecies relating to Christ.
See also: Septuagint: Table of books
In early Christianity the Septuagint was universally used among Greek speakers, while Aramaic Targums were used in the Syriac Church. To this day the Eastern Orthodox Church uses the Septuagint, in an untranslated form. Some scripture of ancient origin is found in the Septuagint but are not in the Hebrew. These include additions to Daniel and Esther. For more information regarding these books, see the articles Biblical apocrypha, Biblical canon, Books of the Bible, and Deuterocanonical books.
Some books that are set apart in the Hebrew text are grouped together. For example the Books of Samuel and the Books of Kings are in the Septuagint one book in four parts called "Of Reigns" (Βασιλειῶν). Scholars believe that this is the original arrangement before the book was divided for readability. In the Septuagint, the Books of Chronicles supplement Reigns and are called Paraleipoménon (Παραλειπομένων—things left out). The Septuagint organizes the minor prophets as twelve parts of one Book of Twelve.
All the books of western canons of the Old Testament are found in the Septuagint, although the order does not always coincide with the modern ordering of the books. The Septuagint order for the Old Testament is evident in the earliest Christian Bibles (5th century).
The New Testament makes a number of allusions to and may quote the additional books (as Orthodox Christians aver). The books are Tobit, Judith, Wisdom of Solomon, Wisdom of Jesus Seirach, Baruch, Epistle of Jeremy (sometimes considered part of Baruch), additions to Daniel (The Prayer of Azarias, the Song of the Three Children, Sosanna and Bel and the Dragon), additions to Esther, 1 Maccabees, 2 Maccabees, 3 Maccabees, 4 Maccabees, 1 Esdras, Odes, including the Prayer of Manasses, and Psalm 151.
See also: Books of the Latin Vulgate.
The canonical Christian Bible was formally established by Bishop Cyril of Jerusalem in 350 and confirmed by the Council of Laodicea in 363, and later established by Athanasius of Alexandria in 367. The Council of Laodicea restricted readings in church to only the canonical books of the Old and New Testaments. The books listed were the 22 books of the Hebrew Bible plus the Book of Baruch and the Epistle of Jeremy, together with the New Testament containing 26 books, omitting the Book of Revelation.
The Council of Carthage, called the third by Denzinger, on 28 August 397 issued a canon of the Bible restricted to: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Josue, Judges, Ruth, 4 books of Kingdoms, 2 books of Paralipomenon, Job, Psalter of David, 5 books of Solomon, 12 books of Prophets, Isaias, Jeremias, Daniel, Ezechiel, Tobias, Judith, Esther, 2 books of Esdras, 2 books of Machabees, and in the New Testament: 4 books of Gospels, 1 book of Acts of the Apostles, 13 letters of the Apostle Paul, 1 of him to the Hebrews, 2 of Peter, 3 of John, 1 of James, 1 of Judas, and the Apocalypse of John.
The canonical acceptance of these books varies among different Christian traditions, and there are canonical books not derived from the Septuagint. For a discussion see the article on Biblical apocrypha.
The exact canon of the Old Testament differs between the various branches of Christianity. All include the books of the Hebrew Bible, while most traditions also recognise several Deuterocanonical books. The Protestant Old Testament is, for the most part, identical with the Hebrew Bible; the differences are minor, dealing only with the arrangement and number of the books. For example, while the Hebrew Bible considers Kings to be a unified text, and Ezra and Nehemiah as a single book, the Protestant Old Testament divides each of these into two books.
Translations of the Old Testament were discouraged in medieval Christendom. An exception was the translation of the Pentateuch ordered by Alfred the Great around 900, and Wyclif's Bible of 1383. Numerous vernacular translations appeared with the Protestant Reformation.
The differences between the Hebrew Bible and other versions of the Old Testament such as the Samaritan Pentateuch, the Syriac, Greek, Latin and other canons, are greater. Many of these canons include whole books and additional sections of books that the others do not. The translations of various words from the original Hebrew may also give rise to significant differences of interpretation.
See main article: Biblical law in Christianity.
Although Christianity by tradition affirms that the Five Books of Moses (the Pentateuch or Torah) is the inspired word of God, Christian tradition denies that all Mosaic Law applies directly to Christians. There are differences of opinion within Christianity as to which laws apply.
Rabbinic Judaism asserts that the Laws of the Jewish Bible were presented to the Jewish people and converts to Judaism and that none of them apply to gentiles, including Christians, with the exception of Noahide Law which applies to all people. Rabbi Emden of the 18th century was of the opinion that Jesus's original objective, and especially Paul's, was only to convert gentiles to Noahide Law while allowing Jews to follow full Mosaic Law.
The New Testament indicates that Jesus Christ mediates a New Covenant relationship between his disciples and God (Luke 22:20; 2Cor 2–3; Heb 8–9). Christianity, almost without exception, teaches that this New Covenant is the instrument through which God offers mercy and atonement to mankind. However, there are differences of opinion as to how the New Covenant affects the validity of biblical law. The differences are mainly as a result of attempts to harmonize biblical statements to the effect that the biblical law is eternal (for example Exodus 31:16-17, 12:14-17) with New Testament statements that suggest that it does not now apply at all, or at least does not fully apply. Most biblical scholars admit the issue of the Law can be confusing and the topic of Paul and the Law is still frequently debated among New Testament scholars (for example, see New Perspective on Paul, Pauline Christianity); hence the various views.
Some conclude that none is applicable, some conclude that only parts are applicable, and some conclude that all is still applicable to believers in Jesus.
The Roman Catholic view is summarised in The Catechism of the Catholic Church: Part 3, Life in Christ: Section 2, The Ten Commandments: "Teacher, what must I do ...?" as follows:
2068 The Council of Trent teaches that the Ten Commandments are obligatory for Christians and that the justified man is still bound to keep them; the Second Vatican Council confirms: 'The bishops, successors of the apostles, receive from the Lord ... the mission of teaching all peoples, and of preaching the Gospel to every creature, so that all men may attain salvation through faith, Baptism and the observance of the Commandments.'
2076 By his life and by his preaching Jesus attested to the permanent validity of the Decalogue.
At the same time, the Roman Catholic Church teaches that the Apostles  instituted the observance of Sunday instead of Saturday, and applies the Third Commandment to Sunday as the day to be kept holy as the Lord's Day. see also Sabbath in Christianity.
The view of the Lutheran Church is summarised in the Formula of Concord which declared (Article V): "We believe, teach, and confess that the distinction between the Law and the Gospel is to be maintained in the Church with great diligence. . ." Martin Luther wrote: "Hence, whoever knows well this art of distinguishing between Law and Gospel, him place at the head and call him a doctor of Holy Scripture."
The distinction between Law and Gospel in the Lutheran view is that Law demands obedience to God's will, while Gospel refers to the promise of forgiveness of sins in the light of the person and work of Jesus Christ.
The Reformed, or Covenant Theology view is similar to the Roman Catholic view. It holds that under the new covenant, the Mosaic Law fundamentally continues, but that parts of it have "expired" and are no longer applicable. The Westminster Confession of Faith (1646) divides the Mosaic laws into three categories: moral, civil, and ceremonial. In the view of the Westminster divines, only the moral laws of the Mosaic Law, which include the Ten Commandments and the commands repeated in the New Testament, directly apply to Christians today. Ceremonial laws, in this view, include the regulations pertaining to ceremonial cleanliness, festivals, diet, and the Levitical priesthood. While the view affirms the Sabbath like the Roman Catholic view, some advocates hold that the Commandment concerning the Sabbath was redefined by Jesus (Matthew 12:1–13, Luke 13:10–17).
In a revival of ideas established in the Puritan period, starting in the 1970s and 1980s, a branch of Reformed theology known as Christian Reconstructionism argued that the civil laws as well as the moral laws should be applied in today's society (a position called Theonomy) as part of establishing a modern theonomic state.
Advocates of this Reformed view hold that, while not always easy to do and overlap between categories does occur, the divisions they make are possible and supported based on information contained in the commands themselves; specifically to whom they are addressed, whom or what they speak about, and their content. For example, a ceremonial law might be addressed to the Levites, speak of purification or holiness and have content which could be considered as a foreshadowing of some aspect of Christ's life or ministry. In keeping with this, most advocates also hold that when the Law is spoken of as everlasting, it is in reference to certain divisions of the Law. Some advocates, usually Theonomists, go further and embrace that idea that the whole Law continues to function, contending that the way in which Christians observe some commands has changed but not the content or meaning of the commands. (For example, they would say that the commands regarding Passover were looking forward to Christ's sacrificial death and the Communion mandate is looking back on it, the former is given to the Levitical priesthood and the latter is given to the priesthood of all believers, but both have the same content and meaning.)   
Those in disagreement with this view claim that nowhere is a division of the Law mentioned in the Bible, but rather there is evidence that it is indivisible, and it would be practically impossible to sort commands by these types. Others in disagreement claim that the Law is described in various places as "everlasting" and none of it can terminate or expire.
The Dispensational view holds that under the new covenant, the Mosaic Law has fundamentally been terminated, or abolished, because, in this view, Scripture never describes the Law as divisible — it is one unit (James 2:10–11). Therefore, because portions of New Testament Scripture (such as Heb. 8:13) are understood in this view to annul at least parts of the Law, then the whole Law must be terminated.
Furthermore, this view holds that the Mosaic laws and the penalties attached to the laws were limited to the particular historical and theological setting of the Old Testament, described in this view as a different "dispensation"; a stage of time in which God dealt with humanity in a fundamentally different way than he does now. We are now living in the "dispensation" of the church/grace, which is a "parenthesis" or "intercalation" in history that is outside of God’s over-arching plan for Israel, and thus the Law given to Israel doesn’t now apply.
Replacing the Mosaic Law is The Law of Christ (Cor 9:21), which holds definite similarities with the Mosaic Law in moral concerns, but is new and different, replacing the first Law. Despite this difference, Dispensationalists may seek to find moral and religious principles applicable for today in all parts of the Mosaic Law.
Those in disagreement with the Dispensational view point out that nowhere does the Bible define a series of "dispensations" that this theology proposes, and point out that God said that he does not change. Furthermore, opponents point out that the Mosaic Law is described in various places as "everlasting" and must fundamentally continue in some form. Others hold that, for this same reason, none at all can terminate or expire.
New Covenant Theology believes that God has maintained one eternal purpose in Christ which has been expressed through a multiplicity of distinct historical covenants; that prominent among these are those designated the Old Covenant (also known as the Mosaic or First Covenant) and the New Covenant; that the former, confined to the people of Israel alone, was established while that nation was assembled before Mt. Sinai and was later made obsolete through its fulfillment by the life and death of Jesus the Messiah; that it was comprised largely of shadows pointing ultimately to Jesus and His body, the Church; and that, therefore, the age in which it remained operative was at all times a period of immaturity as compared to the age of fulfillment which was inaugurated with Christ's first advent.
The Old Covenant, containing a single, unified law code, was a legal, conditional covenant requiring perfect and complete obedience of all those under it; that, on the one hand, it promised life to all who obeyed it, and, on the other hand, it pronounced a curse upon all its transgressors; that it, therefore, inescapably brought death to all who sought to be justified by it—not because of a deficiency in the law (itself "holy, just, and good"), but because of the sinful inability of those under its charge; and that, for this reason, it is variously described as a "killing letter", a "ministry of death", and a "ministry of condemnation"—its distinct purpose being to illumine sin so as to make manifest the Israelites' and, by implication, all men's need for a redeemer.
In contrast to the Old Covenant, the New Covenant (by virtue of Christ's perfect obedience to the law, as well as His bearing of its curse) promises only blessing to all those who belong to it; and that this second covenant, the "everlasting covenant" enacted upon better promises, has thus brought to realization all that was anticipated in the covenants made with Abraham, Moses, and David.
Under the New Covenant, God's people, having entered the age of fulfillment, now stand as mature sons; that having been set free from the tutelage and bondage of the law code written upon tablets of stone, they have subsequently been placed under the Spirit's management—having the new and greater Lawgiver's own law now written upon their hearts.
As a result, though many of the individual commandments given in the Decalogue and the eternal principles upon which the Mosaic Covenant was founded still apply to those under the New Covenant, God's people are now totally free from the Old Covenant as a covenant; that the usefulness of the Mosaic commands is not therefore to be denied, only that these are now understood to come to us through Christ, the mediator of the New Covenant; and that, in particular, with the obsolescence of the Old Covenant, the fourth commandment, the seventh day Sabbath observance, is no longer obligatory—its relevance now pointing to that rest enjoyed by all those in Christ.
The Torah-submissive view, holds that the entire Torah is an indivisible whole and fundamentally continues to apply to all followers of God under the new covenant. Proponents emphasize the Biblical passages in both Old and New Testaments describing God's entire Law as both "everlasting" and "good". In addition, this view holds that, rather than negating the Torah, part of the new covenant is to have this same Torah written upon the hearts of believers by the Holy Spirit. In this view, Jesus, as the sinless son of God and Messiah, could not possibly have transgressed or taught anyone to transgress this God-given Law, but rather Jesus and the New Testament writers reaffirmed all the commands of the Law as a whole (interpreting Matthew 5:17–20, Matthew 23:1–3, Matthew 23:23, etc. to support this stance). In light of these contexts and other Biblical evidence such as prophecy, this view holds different interpretations of the New Testament passages that have traditionally been understood to invalidate parts of the Law. These interpretations are also considered to be based on literary and historical context and examination of the original languages. 
Because of the belief that the Torah is applicable, commands such as dietary laws (not necessarily "kashrut" standards), seventh day Sabbath, and Biblical festival days such as Passover are honored in some way within such segments of Christianity. Not only are they seen as valid commands, but also as valuable teaching tools about Jesus himself and God’s prophetic plan. As with Orthodox Judaism, capital punishment and sacrifice are not practiced because there are strict Biblical conditions on how these are to be properly practiced that are not in place today (although they are supported in principle).
This view affirms that spiritual salvation is by grace through faith in Jesus. It does not hold that any works are a way to achieve justification and hence salvation, but are rather a way of more fully obeying and imitating God as He intended; the same reason for obeying other, traditionally accepted, commands.
Those in disagreement with this view point out the various New Testament scripture passages that seem to negate some or all of the Mosaic Law, suggesting that its "everlasting" nature is subject to modification in some way under the new covenant and that portions of the Mosaic Law were only applicable in a given time and place, for a specific people, or for a limited purpose.
As far as the Ten Commandments, some believe Jesus rejected four of the Ten Commandments and endorsed only Six http://www.beliefnet.com/story/117/story_11719_2.html, citing Mark 10:17–22 and the parallels Matthew 19:16–22 and Luke 18:18–23. (cf. Cafeteria Christianity)
While some Christians from time to time have deduced from statements about the law in the writings of the Apostle Paul that Christians are under grace to the exclusion of all law (see antinomianism, hyperdispensationalism, Christian anarchism), this is not the usual viewpoint of Christians.
The Acts of the Apostles in the New Testament describes a conflict among the first Christians as to the necessity of following all the laws of the Torah to the letter, see Council of Jerusalem.
Some have interpreted Mark's statement: "Thus he declared all foods clean" (Mark 7:19 NRSV) to mean that Jesus taught that the pentateuchal food laws were no longer applicable to his followers, see also Antinomianism in the New Testament. However, the statement is not found in the Matthean parallel Matthew 15:15–20 and is also a disputed translation: the Scholars Version has: "This is how everything we eat is purified", Gaus' Unvarnished New Testament has: "purging all that is eaten." See also Strong's G2511.
Others note that Peter had never eaten anything that was not kosher many years after Acts 2 (Pentecost). To the heavenly vision he announced: "Not so, Lord; for I have never eaten any thing that is common or unclean." (Acts 10:14) Therefore, Peter was unaware that Jesus had changed the Mosaic food laws. In Mark 7, Jesus may have been just referring to a tradition of the Pharisees about eating with unwashed hands. For example, the insertion found in many translations concerning his declaration that all foods were clean is not found in the King James Version: Mark 7:19. The expression "purging all meats" may have meant the digestion and elimination of food from the body rather than the declaration that all foods were kosher. The confusion primarily centers around the participle used in the original Greek for "purging". Some scholars believe it agrees with the word for Jesus, which is nearly 40 words away from the participle. If this is the case, then it would mean that Jesus himself is the one doing the purifying. In New Testament Greek, however, the participle is rarely that far away from the noun it modifies, and many scholars agree that it is far more likely that the participle is modifying the digestive process (literally: the latrine), which is only two words away. The writer of Hebrews indicates that the sacrifices and the Levitical priesthood foreshadowed Jesus Christ's offering of himself as the sacrifice for sin on the Cross, and many have interpreted this to mean that once the reality of Christ has come, the shadows of the ritual laws cease to be obligatory (Heb 8:5; 9:23–26; 10:1). On the other hand, the New Testament repeats and applies to Christians a number of Old Testament laws, including "Love your neighbor as yourself" (Lev 19:18; cf. Golden Rule, Mark 12:31), "Love the LORD your God with all your heart, soul and strength" (Deut 6:4–5, the Shema, Mark 12:29–30).
Still others believe a partial list of the commandments was merely an abbreviation that stood for all the commandments because Jesus prefaced his statement to the rich young ruler with the statement: "If you want to enter life, obey the commandments." Some people claim that since Jesus did not qualify his pronouncement, that he meant all the commandments. The rich young ruler asked "which" commandments. Jesus gave him a partial list from the second table. The first set of commandments deal with a relationship to God. The second set of commandments deal with a relationship to men. No doubt Jesus considered the relationship to God important, but Jesus may have considered that the young man was perhaps lacking in this second set, which made him obligated to men. (This is inferred by his statement that to be perfect he should sell his goods, give them to the poor and come and follow Jesus—thereby opening to him a place in the coming Kingdom.)
Several times Paul mentioned adhering to "the Law", such as Romans 2:12–16, 3:31, 7:12, 8:7–8, Gal 5:3, Acts 24:14, 25:8 and preached about Ten Commandment topics such as idolatry (Cor 5:11, 6:9–10, 10:7, 10:14, Gal 5:19–21, Eph 5:5, Col 3:5, Acts 17:16–21, 19:23–41). Many Christians believe that the Sermon on the Mount is a form of commentary on the Ten Commandments. In the Expounding of the Law, Jesus said that he did not come to abolish the Law, but to fulfill it; while in Marcion's version of Luke 23:2 we find the extension: "We found this fellow perverting the nation and destroying the law and the prophets". See also Adherence to the Law and Antithesis of the Law.
Current debate concerning the historicity of the various Old Testament narratives can be divided into several camps.
The vast majority of scholars at American universities are somewhere between biblical minimalism and maximalism.
Notably, both Kitchen and archaeologist Israel Finkelstein of Tel Aviv University are not the only scholars from the maximalist and minimalist camps who are sufficiently trained to address these questions with the necessary sophistication but both are experts in their fields—and both come to different conclusions.
Some contemporary Israeli archaeologists have now rejected much of the Deuteronomistic history of the Old Testament. Notably, Finkelstein and Neal Asher Silberman have written popular books detailing their view that many of the best-known Biblical stories are incompatible with the archaeology of the region. Conversely, in 2003 Kenneth A. Kitchen published the 662 page book On the Reliability of the Old Testament, which defended the Bible's reliability throughout. Although some archaeologists have argued that many Biblical accounts should be rejected due to a lack of corroborating archaeological evidence, opponents point out that this is a return to the 19th century idea that anything not confirmed by current archaeology should be dismissed, a methodology that had once led some to question the existence of major empires such as Assyria.
Because the composition of the Pentateuch according to Wellhausen was so much later than the events it described, some who accept Wellhausen's documentary hypothesis tend to regard the narratives of the Pentateuch as largely fictional, while others argue that Wellhausen's method is not valid given that so many of our surviving copies of historical documents date from a much later time period: e.g., the earliest extant copies of Julius Caesar's famous "Commentaries on the Gallic War" are medieval copies dating from the 9th century, nearly a thousand years after Caesar wrote the original.
The most important issue would seem to be the length of the period between the actual events and the setting of them down in writing. Internal evidence in the books themselves suggests that events of the Hebrew monarchies period were set down by royal scribes soon after they happened, and the writer(s) of the Book of Kings had direct access to these writings and quoted extensively from them—whereas earlier events, such as the Exodus and the Conquest, might have spent centuries as oral traditions before a written account of them was set down, which might make the written account considerably different from any actual events that gave the original basis to the tradition.
Umberto Cassuto wrote The Documentary Hypothesis, challenging Wellhausen's theory.
See also Dead Sea scrolls in which a copy of the book of Isaiah has been radiocarbon dated by the University of Arizona Department of Physics to between 335 BCE and 122 BCE.http://www.physics.arizona.edu/physics/public/dead-sea.html