A.T. Robertson Commentary Romans 12:14

"Bless them that persecute you; bless, and curse not." — Romans 12:14 (ASV)

And curse not (κα μη καταρασθε). Present middle imperative with μη. Like Mt 5:44 in spirit, not a quotation, but a reminiscence of the words of Jesus. The negative addition gives emphasis. See Lu 6:28 for the old verb καταραομα from καταρα (curse).