A.T. Robertson Commentary James 2:11

"For he that said, Do not commit adultery, said also, Do not kill. Now if thou dost not commit adultery, but killest, thou art become a transgressor of the law." — James 2:11 (ASV)

He that said (ο ειπων)

--said also (ειπεν κα). The unity of the law lies in the Lawgiver who spoke both prohibitions (μη and the aorist active subjunctive in each one, μοιχευσηισ, φονευσηις). The order here is that of B in Ex 20 (Luke 18:20; Romans 13:9), but not in Mt 5:21,27 (with ου and future indicative).

Now if thou dost not commit adultery, but killest (ε δε ου μοιχευεισ, φονευεις δε). Condition of first class with ου (not μη) because of the contrast with δε, whereas ε μη would mean "unless," a different idea. So ου in 1:23.

A transgressor of the law (παραβατης νομου) as in verse 9. Murder springs out of anger (Matthew 5:21–26). People free from fleshly sins have often "made their condemnation of fleshly sins an excuse for indulgence towards spiritual sins" (Hort).