Martin Luther (10 November 1483 – 18 February 1546) initiated the Protestant Reformation. As a priest and theology professor, he confronted indulgence salesman Johann Tetzel with his The Ninety-Five Theses in 1517. Luther strongly disputed their claim that freedom from God's punishment of sin could be purchased with money. His refusal to retract all of his writings at the demand of Pope Leo X in 1520 and the Holy Roman Emperor Charles V at the Diet of Worms in 1521 resulted in his excommunication by the pope and condemnation as an outlaw by the emperor. Martin Luther taught that salvation is not from good works, but a free gift of God, received only by grace through faith in Jesus as redeemer from sin. His theology challenged the authority of the pope of the Roman Catholic Church by teaching that the Bible is the only source of divinely revealed knowledge and opposed sacerdotalism by considering all baptised Christians to be a holy priesthood. Those who identify with Luther's teachings are called Lutherans.