John Calvin 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)

For he that said, or he who has said. This is a proof of the previous verse, because the Lawgiver is to be considered rather than each particular precept apart. The righteousness of God, as an indivisible body, is contained in the law.

Whoever, then, transgresses one article of the Law, destroys, as far as he can, the righteousness of God. Besides, as in one part, so in every part, it is God’s will to test our obedience.

Therefore, a transgressor of the law is everyone who offends concerning any one of its commandments, according to this saying: Cursed is he who fulfills not all things (Deuteronomy 27:26).

We further see that the transgressor of the law, and the one guilty of all, mean the same thing according to James.