Letters (Epistulae)

...by destroying [those things] which had been constructed, just as Josiah served by doing such things himself; 4 Kgs 23:4-20 just as the king of the Ninevites served by compelling the entire city to appease the Lord; Jon 3:6-9 just as Darius served by giving into the power of Daniel the idol to be broken and by casting his enemies to the lions; Dan 14:21; 41 just as Nebuchadnezzar, of whom we have already spoken, served by prohibiting all those situated in his kingdom from blaspheming God by a terrible law. Dan 3:96 In this, therefore, kings serve the Lord, in so far as they are kings, when they do those things to serve Him which only kings can do. VI

When, therefore, kings did not yet serve the Lord in the times of the apostles, but still meditated on vain things against Him and against His Christ, so that all the predictions of the prophets might be fulfilled, they could not, of course, prohibit impieties by laws, but rather exercised them. For the order of the times was unfolding in such a way that the Jews killed the preachers of Christ, thinking they were doing a service to God, just as Christ had predicted, and the nations raged against the Christians, and the patience of the martyrs overcame all. But after that which is written began to be fulfilled:

"And all the kings of the earth shall adore Him: all nations shall serve Him," Ps 71:11

who in his right mind could say to kings: 'Do not concern yourselves in your kingdom with how the Church of your Lord is held or attacked; it should not pertain to you who wishes to be religious or sacrilegious,' when to them it cannot be said: 'It does not pertain to you, in your kingdom, who wishes to be chaste or unchaste?'