It was in the course of the year 1520—as we have already seen—that the civil authorities of Zurich first interfered with the work of the Reformation. The effect produced upon the middle and lower classes by the preaching of Zwingle then began to display itself. In addition to the subject of Lent, which then came before the senate, through the edict of the bishop of Constance, Zwingle called the attention of the Zurichers to the gross licentiousness which prevailed in Switzerland through the celibacy of the clergy; and in a private letter to the bishop he entreated him not to promulgate any edict injurious to the gospel, nor any longer to tolerate fornication, nor to enforce the celibacy of the priesthood. "In some of the cantons the priests were required to keep concubines, and everywhere that practice was permitted for money." Instead, however, of listening to the needed and respectful remonstrance of the Reformer, the bishop began to persecute several of the clergy who were known to have embraced the new opinions. They were branded as Lutheran heretics, and denounced as holding opinions hostile to the See of Rome. Until this time the Swiss Reformers had not met with any public or systematic opposition: but now, the church implored the state to interfere and arrest their progress everywhere.
But under the good providence of God, the opposition which now arose in so many quarters was overruled for the deepening and the extension of the work. The controversies and the public disputations were eminently used in Switzerland for the furtherance of the Reformation. The wind of persecution but scattered the good seed of the kingdom, and caused it to take root all over the land. "The priests stood up," says the Swiss historian, "as in the days of the apostles, against the new doctrines. Without these attacks, it would probably have remained hidden and obscure in a few faithful souls. But God was watching the hour to manifest it to the world. Opposition opened new roads for it, launched it on a new career, and fixed the eyes of the nations upon it. The tree that was destined to shelter the people of Switzerland had been deeply planted in her valleys, but storms were necessary to strengthen its roots and extend its branches. The partisans of the papacy, seeing the fire already smoldering in Zurich, rushed forward to extinguish it, but they only made the conflagration fiercer and more extensive."