Tertullian · a new plain-English translation from the original language
There is another, greater necessity laid on us to pray for the emperors—indeed for the whole condition of the empire and for the affairs of Rome—because we know that the immense catastrophe threatening the entire world, the very last convulsion bringing on its train of horrors, is held back by the continuance of the Roman empire. So we have no wish to experience that day, and by praying for its postponement we are lending our support to Rome's long survival.
But we do swear—not by the geniuses of the Caesars, but by their welfare, which is a thing more august than any genius. Don't you know that "geniuses" is just another word for demons, and from that comes the diminutive term "demonias"? We look up instead to God's judgment resting on the emperors, since it is he who placed them at the head of the nations. We know that whatever is in them is what God willed, and so we too wish safe what God has willed—and we hold that as a great oath indeed. As for demons, that is, geniuses, our custom is to adjure them—to drive them out of men—not to swear by them, as though conferring on them the honor due to divinity.