Indulgences, contrary to popular opinion are not the buying of time off purgatory.
Indulgences are "the remission before God of the temporal punishment due for sins already forgiven as far as their guilt is concerned." (Enchiridion of Indulgences) This remission of sin is not done under our own power. The sin, in this case, has already been forgiven (see the requirement of confession for an indulgence, below.) The grace comes from Jesus' sacrifice on the cross.
The requirements for an indulgence to be granted are:
- the faithful must receive the sacrament of confession, either eight days before or after the pious act is performed,
- receive Holy Communion on that day
- and recite prayers for the intentions of the Holy Father (one Our Father and one Hail Mary is the minimum, but any other additional prayers may be added).
The selling of indulgences did occur during Luther's time. It was one of Luther's chief arguments against the Church. Selling of indulgences is NOT in line with Church teaching and was done by unscrupulous members of the clergy during Luther's day. The resulting schism goes to show how serious such scandalous acts are. Indeed, Jesus said, "Whoever causes one of these little ones who believe in Me to stumble, it would be better for him to have a heavy millstone hung around his neck, and to be drowned in the depth of the sea." (Matthew 18:6)