His birth name was Jodokus (Jobst) Koch, which he changed according to the common custom of German scholars in the sixteenth century, when at the University of Erfurt.

[5] His great admiration for Erasmus first led him to Greek, Hebrew and Biblical studies, and his election in May 1519 as rector of the university was regarded as a triumph for the partisans of the New Learning.

He accompanied Luther to the Diet of Worms in 1521, and there was appointed professor of canon law at Wittenberg.

Giving himself up to preaching and polemics, he aided the Reformation by his gift as a translator, turning Luther's and Melanchthon's works into German or Latin as the case might be, thus becoming a sort of double of both.

[7] His hymn Wo Gott der Herr nicht bei uns hält, a paraphrase of Psalm 124, was published in the Erfurt Enchiridion in 1524.

[4] In the autumn of 1531, Jonas published a German translation of the Apology of the Augsburg Confession, and in 1541, he began a successful preaching crusade in Halle, becoming superintendent of its churches in 1542 or 1544 and priest in the Market Church of Our Dear Lady (Marktkirche Unser Lieben Frauen) the city of Halle, Saxony-Anhalt.