A.T. Robertson Commentary Romans 13:3

"For rulers are not a terror to the good work, but to the evil. And wouldest thou have no fear of the power? do that which is good, and thou shalt have praise from the same:" — Romans 13:3 (ASV)

A terror (φοβος). This meaning in Isa 8:13. Paul does not approve all that rulers do, but he is speaking generally of the ideal before rulers. Nero was Emperor at this time.

From the same (εξ αυτης). "From it" (εξουσια, personified in verse 4).