On the 30th of April in 1526 Zwingli published Uber den ungesandten Sandbrieff Joannes Fabers Doctors an Huldrychen Zvinglin geschriben und hinderwert usgespreyt und nit überschickt / Antwurt Huldrychs Zvinglis.
Faber and Zwingli had a checkered history – at first being in essential agreement concerning the sale of indulgences (which both opposed) but then disagreeing about every other aspect of Zwingli’s reformatory efforts. Faber was the Vicar General of Constance and the Bishop’s right hand man. As the Encyclopedia Britannica observes
In 1518 Hugo von Landenberg, bishop of Constance, made him one of his vicars-general, and Pope Leo X. appointed him papal protonotary. He was an advocate of reforms, in sympathy with Erasmus, and corresponded (1519-1520) with Zwingli. While he defended Luther against Eck, he was as little inclined to adopt the position of Luther as of Carlstadt. His journey to Rome in the autumn of 1521 had the result of estranging him from the views of the Protestant leaders. He published Opus adversus nova quaedam dogmata Lutheri (1522), and appeared as a disputant against Zwingli at Zurich (1523). Then followed his Malleus in haeresin Lutheranam (1524). Among his efforts to stem the tide of Protestant innovation was the establishment of a traininghouse for the maintenance and instruction of popular preachers, drawn from the lower ranks, to compete with the orators of reform. In 1526 he became court preacher to the emperor Ferdinand, and in 1527 and 1528 was sent by him as envoy to Spain and England. He approved the death by burning of Balthasar Hubmeier, the Baptist, at Vienna on the 10th of March 1528. In 1531 he was consecrated bishop of Vienna, and combined with this (till 1538) the administration of the diocese of Neustadt. He died at Vienna on the 21st of May 1541. His works were collected in three volumes, 1537, 1539 and 1541.