For. This introduces the reason for the previous declaration. Since the state exists as a servant of God for a good purpose, the Christian has no cause to fear its authority if he leads a peaceable life. Here again Paul is expressing a general truth, not tarrying to qualify his statement with specific exceptions.
He. Or, “it,” referring to “the power,” “the authority,” in v. 3.
Minister. Gr. diakonos, “servant” (see ch. 15:8; 16:1). Diakonos is also the word used to describe the office of the deacon (1 Tim. 3:8, 12).
To thee. That is, for your advantage, in your interest.
For good. That is, to promote good. This is the true reason for the existence of civil government, as the servant and representative of God.
The sword. The symbol of the ruler’s authority to inflict punishment.
A revenger. Gr. ekdikos, “an avenger.” The only other NT occurrence of this word is in 1 Thess. 4:6. In the Greek papyri this term is generally used for “a legal representative.”
To execute wrath. Literally, “for wrath.” As “the minister of God” the state is to inflict punishment on evildoers (cf. v. 2; ch. 12:19).