Calvin on the Duties of the Civil Magistrate

The duty of magistrates, its nature, as described by the word of God, and the things in which it consists, I will here indicate in passing. That it extends to both tables of the law, did Scripture not teach, we might learn from profane writers, for no man has discoursed of the duty of magistrates, the enacting of laws, and the common weal, without beginning with religion and divine worship. Thus all have confessed that no polity can be successfully established unless piety be its first care, and that those laws are absurd which disregard the rights of God, and consult only for men.

[continued]

John Calvin, Institutes, IV:20:9