Luther's ninety five theses originated with an epiphany Luther had when his confessor suggested he read Paul's Epistle to the Romans. Luther keyed on a particular verse in Romans 1:17: "the just shall live by faith." From this, Luther determined that faith alone was necessary for one to achieve salvation. The Church's position had been that good works were also necessary (together with faith.) The church taught that a "treasury of merit" had been accrued by Jesus and the Saints, and this excess merit could be redistributed by the Pope or his emissary to those who needed a good work. These were "indulgences" which in Luther's day were offered for sale.
The specific instance which caused Luther's objection was the sale of Indulgences by one Johan Tetzel,a Dominican friar, who was raising money to repay a loan used by Pope Leo X to build the basilica at St. Peter's Cathedral in Rome. Tetzel zealously hawked his indulgences, even including his own ditty:
As soon as a coin in the coffer rings.
Another soul from purgatory rings.
Tetzel even went so far as to producing a chart which showed the amount needed to achieve forgiveness for certain sins. Luther saw this as selling salvation, which undermined penance. Contrary to popular belief, Luther did not nail his theses to the Church door, but rather mailed them to Archbishop Albert of Mainz. They were soon published in German throughout the Holy Roman Empire. They provide in part:
The penitential canons apply only to men who are still alive, and, according to the canons themselves, none applies to the dead.
Accordingly, the Holy Spirit, acting in the person of the pope, manifests grace to us, by the fact that the papal regulations always cease to apply at death, or in any hard case.
It is a wrongful act, due to ignorance, when priests retain the canonical penalties on the dead in purgatory.
Hence those who preach indulgences are in error when they say that a man is absolved and saved from every penalty by the pope's indulgences.
Indeed, he cannot remit to souls in purgatory any penalty which canon law declares should be suffered in the present life.
There is no divine authority for preaching that the soul flies out of the purgatory immediately the money clinks in the bottom of the chest.
It is certainly possible that when the money clinks in the bottom of the chest avarice and greed increase; but when the church offers intercession, all depends in the will of God.
It is not in accordance with Christian doctrines to preach and teach that those who buy off souls, or purchase confessional licenses, have no need to repent of their own sins.
Any Christian whatsoever, who is truly repentant, enjoys plenary remission from penalty and guilt, and this is given him without letters of indulgence.
Any true Christian whatsoever, living or dead, participates in all the benefits of Christ and the Church; and this participation is granted to him by God without letters of indulgence.