John Chrysostom
Then, after fear, the Apostle proves the benefit of obedience and persuades on the basis of rational arguments, saying, “For rulers are not a terror to good works, but to evil.” First he struck a strong blow and brought his hearers into fear. Now he again gives relief and, like a wise physician, administers a soothing medicine. He comforts them and says: why are you afraid? Why are you terrified? Does the ruler punish the one who does good? Is he terrible to one who cares for virtue? Therefore the Apostle also adds, “Do you want to be unafraid of the authority? Do what is good, and you will have praise from him.” Do you see how he reconciled the one who does good with the ruler, showing that the ruler has been appointed to praise him? Do you see how he removed every anger? See verse 4.