Oecolampadius returned to Basel in November 1522, as vicar of St Martin's, and (in 1523) reader of the Holy Scripture at the University of Basel. Lecturing on Isaiah, he condemned current ecclesiastical abuses, and in a public disputation (20 August 1523) gained such success that Erasmus writing to Zürich said, "Oecolampadius has the upper hand amongst us." He became Huldrych Zwingli's loyal friend and ally, and after more than a year of earnest preaching and four public disputations in which the popular verdict went in favour of Oecolampadius and his friends, the authorities of Basel began to see the need for Reformation.
