Peter’s, and papal emissaries sought everywhere to raise funds by thesale of indulgences. The system was grossly abused, and Luther’sindignation at the shameless traffic, carried on in particular by theDominican Johann Tetzel, became irrepressible. As professor of biblicalexegesis at Wittenberg (1512–46), he began to preach the doctrine ofsalvation by faith rather than works; and on 31 October 1517 drew up alist of 95 theses on indulgences denying the pope any right to forgivesins, and nailed them on the church door at Wittenberg. Tetzel retreatedfrom Saxony to Frankfurt-an-der-Oder, where he published a set of counter-theses and burnt Luther’s. The Wittenberg students retaliated by burningTetzel’s, and in 1518 Luther was joined in his views by Melanchthon.