Shocked by the indulgence trade established by Popes Julius II and Leo X to finance the construction of St. Peter's Basilica in Rome, he published the 95 Theses on October 31, 1517.
Summoned on June 15, 1520, by Pope Leo X to retract his statements, he was excommunicated on January 3, 1521, by the papal bull Decet Romanum Pontificem. The Holy Roman Emperor and King of Spain, Charles V, summoned Martin Luther in 1521 to the Diet of Worms. A safe conduct was granted to him to attend without risk.
Before the Diet of Worms, he refused to retract, declaring himself convinced by the testimony of Scripture and feeling bound by the authority of the Bible and his conscience rather than that of the ecclesiastical hierarchy. The Diet of Worms, under pressure from Charles V, then decided to put Martin Luther and his followers under the ban of the Empire.
He was welcomed by his friend, the Elector of Saxony Frederick III the Wise, at the Wartburg Castle, where he composed his most well-known and widely distributed texts. It was there that he embarked on a translation of the Bible into German from the original texts, a translation whose cultural influence would be paramount, both for the establishment of the German language and for the establishment of the principles of the art of translation.