Simony is the ecclesiastical crime of paying for holy offices or positions in the hierarchy of a church, named after Simon Magus, who appears in the Acts of the Apostles 8:18-24. Simon Magus offers the disciples of Jesus, Peter and John, payment so that anyone he would place his hands on would receive the power of the Holy Spirit. This is the origin of the term simony but it also extends to other forms of trafficking for money in "spiritual things". 
The intertwining of temporal with spiritual authority in the Middle Ages caused endless problems with simony and accusations of simony. Secular rulers wanted to employ the educated and centrally organized clergy in their administrations, and often treated their spiritual positions as adjuncts to the secular administrative roles.
Canon Law also outlawed as simony some acts that did not involve the sale of offices, but the sale of spiritual authority: the sale of tithes, the taking of a fee for confession, absolution, marriage or burial, and the concealment of one in mortal sin or the reconcilement of an impenitent for the sake of gain. Just what was or was not simony was strenuously litigated: as one commentator notes, the widespread practice of simony is best evidenced by the number of reported ecclesiastical decisions as to what is or is not simony.
Simony did serious harm to the moral standing of the Roman Catholic Church. Dante Alighieri condemns simonists to the eighth circle of hell in his Inferno, where he encounters Pope Nicholas III buried upside down, the soles of his feet burning with oil, in a mock baptism. Dante goes on to predict the damnation of both Pope Boniface VIII, the Pope in office at the time the Divine Comedy is set, and Pope Clement V, his successor, for that sin. Writers in the early Renaissance, such as Niccolò Machiavelli and Erasmus, condemned the practice, while Blaise Pascal attacked the casuistic defenses offered by those accused of simony in his Lettres provinciales.
The Church of England also struggled with the practice after its separation from Rome. While English law recognized simony as an offence, it treated it as merely an ecclesiastical matter, rather than a crime, for which the punishment was forfeiture of the office or any advantage from the offence and severance of any patronage relationship with the person who bestowed the office. The cases of Bishop of St. David's Thomas Watson in 1699 and of Dean of York William Cockburn in 1841 were particularly notable.
, simony remains an offence.  An unlawfully bestowed office can be declared void by the Crown, and the offender can be disabled from making future appointments and fined up to £1000. Clergy are no longer required to make a declaration as to simony on ordination but offences are now likely to be dealt with under the Clergy Discipline Measure 2003, r.8.