Albert Barnes on Romans 13:5

Wherefore, (διο). The reasons why we should be subject, which the apostle had given, were two:

(1.) That government was appointed by God.

(2.) That violation of the laws would necessarily expose to punishment.

Ye must needs be. It is necessary (αναγκη) to be. This is a word stronger than that which implies mere fitness or propriety. It means, that it is a matter of high obligation and of necessity to be subject to the civil ruler.

Not only for wrath. Not only on account of the fear of punishment; or the fact that wrath will be executed on evil doers.

For conscience' sake. As a matter of conscience, or of duty to God, because he has appointed it, and made it necessary and proper. A good citizen yields obedience because it is the will of God; and a Christian makes it a part of his religion to maintain and obey the just laws of the land. See Mt 22:21. Comp. Eccl 8:2, "I counsel them to keep the king's commandments, and that in regard of the oath of God."

(y) "ye must needs be subject" Ex 8:2