Paul therefore reasoneth here, out of a plain testimony of the prophet, that there is none which obtaineth
justification and life before God, but the believing man, who obtaineth righteousness and everlasting life without the law, and without charity, by faith alone. The reason is, because the law is not of faith, or anything belonging to faith, for it believeth not: neither are the works of the law faith, nor yet of faith: therefore faith is a thing much differing from the law. For the promise is not apprehended by working, but by believing.
Martin Luther, Kregel, Galatians 3:12, p. 159.
KJV Galatians 3:11 But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith. 12 And the law is not of faith: but, The man that doeth them shall live in them.