Answer:
Martin Luther was a German theologian who started the Protestant Reformation in the early-1500s, criticizing the policies carried out by the Catholic Church, especially the sale of indulgences and the political powers that the Pope and the main bishops of the European nations had adopted.
Regarding indulgences and their sale, Luther criticized that the Catholic Church granted God's forgiveness only to those who had the economic possibility of buying it, leaving aside issues such as the sinner's true repentance, or the worth of people who did not have the same economic possibility than the rich.