Letters (Epistulae)

more should a man not be abandoned by a man, and a brother by a brother, so that he may not perish eternally, he who, once corrected, can understand what a great benefit was being bestowed upon him when he was complaining that he was suffering persecution!
8 Therefore, as the apostle says: "Let us not grow weary while we have time, in doing good to all." Those who can be called to salvation by the sermons of Catholic preachers, those who can be called by the laws of Catholic princes—partly by those who obey divine admonitions, partly by those who obey imperial commands—let all be called to salvation, all be recalled from ruin. For even when emperors enact bad laws for falsehood against the truth, those who believe well are proven and those who persevere are crowned; but when they enact good laws for the truth against falsehood, those who rage are terrified and those who understand are corrected. Whoever, therefore, does not wish to obey the laws of emperors which are made against the truth of God, earns a great reward; but whoever does not wish to obey the laws of emperors which are made for the truth of God, earns a great punishment. For even in the times of the prophets, all the kings who in the people of God did not forbid nor overturn what had been instituted against the commandment of God are blamed, and those who forbade and overturned are praised above the merits of others. And King Nebuchadnezzar, while he was a servant of idols, enacted a sacrilegious law that an image should be worshipped; but those who did not wish to obey his impious constitution acted piously and faithfully. That same king, however, corrected by a divine miracle, enacted a pious and praiseworthy law for the truth, that whoever should speak blasphemy against the true God...

Scriptural references: Gal 6:9-10; Dan 3:5, 96 (referring to Nebuchadnezzar's decree).