From his lectures on the Psalms Luther proceeded a few years later to an exposition of those Epistles which were to him the main source of his new belief in God's mercy and justice, namely, the Epistles to the Romans and the Galatians.
In the convent also at Wittenberg, the direction of the theological studies of the brethren was entrusted to Luther. His fellow-labourer in this field was his friend John Lange, who had been with him also in the convent at Erfurt. He was distinguished for a rare knowledge of Greek, and was therefore a valuable help even to Luther, to whom he was indebted in turn for a prolific advance in learning of another kind. Closely allied with Luther also was Wenzeslaus Link, the prior of the convent, who obtained his degree as doctor of the theological faculty a year before him. These men were drawn together by similarity of ideas, and by a strong and enduring personal friendship; they had possibly been acquainted at the school at Magdeburg. The new life and activity awakened at Wittenberg attracted clever young monks more and more from a distance. The convent, not yet quite finished, had scarcely room enough for them, or means for their maintenance.
When in 1515 the associated convents had to choose at Gotha, on a chapter-day, their new authorities, Luther was appointed, Staupitz being still Vicar-General, the Provincial Vicar for Meissen and Thuringia. He obtained by this office the superintendence of eleven convents, to which in the next year he paid the customary visitation. In person, by word of mouth, and equally by letters, we see him labouring with self-sacrificing zeal for the spiritual welfare of those committed to his care, for the correction of bad monks, for the comfort of those oppressed with temptations, as also for the temporal and domestic, and even the legal business of the different convents.
In addition to his academical duties, he performed double service as a preacher. In the first place he had to preach in his convent, as he had already done at Erfurt. When the new convent at Wittenberg was opened, the church was not yet ready; and in a small, poor, tumbledown chapel close by, made up of wood and clay, he began to preach the gospel and unfold the power of his eloquence. When, shortly after, the town-priest of Wittenberg became weak and ailing, his congregation pressed Luther to occupy the pulpit in his place. He performed these different duties with alacrity, energy, and power. He would preach sometimes daily for a week together, sometimes even three times in one day; during Lent in 1517 he gave two sermons every day in addition to his lectures at the university. The zeal which he displayed in proclaiming the gospel to his hearers in church, was quite as new and peculiar to himself as the lofty interest he imparted to his professorial lectures on the Scriptures.