Was the practice taught? Was it encouraged? Did one person go away thinking he had done that which is right by the Lord because the Pope said it was right? Remember what Paul taught. That which I do, put into practice. If the Pope encouraged it, it was practiced, desired, and in ERROR.
What is the reason for indulgences? Forgiving of sins? Only Jesus can forgive a sin, not a Pope, not Mary, not a Saint, nobody but Jesus, and he don't need your money to do it.
As far as I can tell from the historical record, the practice did not appear until 1517, when Pope Leo X offered indulgences for those who helped the rebuilding of St. Peter's Basilica. It wasn't a teaching, but as I said, a practice. His practice was officially rebuked by the Council of Trent, later in the same century.
What is the reason for indulgences? Forgiving of sins?
An indulgence is for the remission of temporal punishments for sins already forgiven.
Only Jesus can forgive a sin, not a Pope, not Mary, not a Saint, nobody but Jesus, and he don't need your money to do it.
The Church has never taught that Mary or any of the saints can forgive sins. The power of priests to grant absolution of sins is Scriptural. "When he had said this, he breathed on them; and he said to them: Receive ye the Holy Ghost. Whose sins you shall forgive, they are forgiven them; and whose sins you shall retain, they are retained" (John 20: 22-23).