The Reformer was no doubt warmly welcomed by the party inside the castle, and earnestly entreated to become one of their preachers. These solicitations he steadfastly resisted, "alleging that he could not run where God had not sent him." When he received a unanimous invitation from the whole congregation, and was solemnly pressed by Mr. Rough, a preacher, not to refuse God's call as he would avoid His heavy displeasure, Knox burst into tears, and withdrew himself to his chamber. He had now very different thoughts as to the importance of the ministerial office, from what he had entertained when invested with priest's orders. The charge of declaring "the whole counsel of God, keeping nothing back," however ungrateful it might be to his hearers, with all the consequences to which the preachers of the Protestant doctrines were then exposed, filled his mind with anxiety and fear. He evidently passed through much conflict of mind on this occasion; for though he possessed great strength of character, being naturally bold, upright, and independent, he was thoroughly honest, conscientious, and modest. But when he felt satisfied that he had the call of God to engage in His work, he resolved to undertake it with all its responsibilities, and say with the apostle, "But none of these things move me, neither count I my life dear unto myself, so that I might finish my course with joy, and the ministry, which I have received of the Lord Jesus, to testify the gospel of the grace of God." (Acts 20:2424But none of these things move me, neither count I my life dear unto myself, so that I might finish my course with joy, and the ministry, which I have received of the Lord Jesus, to testify the gospel of the grace of God. (Acts 20:24).)
He commenced his labors as a preacher with his characteristic boldness, and was greatly blessed both to the garrison and to the inhabitants of the town. In his first sermon in the parish church of St. Andrew's, he undertook to prove that the pope of Rome was the man of sin, the Antichrist, the Babylonish harlot spoken of in scripture. He struck at the root of popery that they might destroy the whole system. During the few months that he preached at St. Andrew's, a great number of the inhabitants, besides the garrison in the castle, renounced popery, and made profession of the Protestant faith, by partaking of the Lord's supper after the Reformed mode in Scotland. But his useful labors were soon interrupted.