Literally, “law” (see on ch. 2:12). Although his references to particular commands is the Decalogue (ch. 13:9) indicate that Paul has that law especially in mind, the absence of the article “the” with “law” suggests that he may be speaking of “law” as a principle. As sin is disobedience to law, or lawlessness (see on 1 John 3:4), so on the contrary love is, literally, “the fulfillment of law” (Rom. 13:10).

 He who loves his fellow men has carried out the intent and purpose of the law. All the commandments of God are based upon the one principle of love (Matt. 22:34-40; cf. Rom. 13:9). Therefore, His law cannot be perfectly obeyed by mere outward conformity to the letter. True obedience is a matter of the heart and of the spirit (cf. Rom. 2:28, 29). Not external compliance but heartfelt love is the fulfillment of the law (ch. 13:10). This fundamental truth the Jews had been slow to believe and practice, despite the clear teachings of Moses on the subject (see Lev. 19:18, 34; Deut. 6:5; 10:12). They turned God’s law of love into a rigid and loveless code of legal requirements. They were quick to tithe even the mint and anise and cummin, but passed over the weightier matters of the law, faith, judgment, mercy, and the love of God (Matt. 23:23; Luke 11:42). Therefore Jesus sought to reveal once again the true purpose of His Father’s commandments. He taught that all the commands are summed up in love (Matt. 22:37-40; Mark 12:29-34; Luke 10:27, 28), and that the distinguishing mark of an obedient disciple is love for his fellow men (John 13:34, 35).

Literally, “loveth the other.” Hence the translation “his neighbor” (RSV).

Mutual love is an infinite obligation. It is a debt that one should ever be seeking to discharge but that will never be fully paid so long as there remains an opportunity for doing good to one’s fellow men.

The Christian is to pay all he owes, but there is one debt he can never fully meet, namely, the debt of love to his fellow men.