Charles Ellicott Commentary Galatians 3:21

"Is the law then against the promises of God? God forbid: for if there had been a law given which could make alive, verily righteousness would have been of the law." — Galatians 3:21 (ASV)

The promises.—Here, as in Galatians 3:16, the plural, because the promise to Abraham was several times repeated, and afterwards ratified to his descendants.

For if . . .—The argument which follows begins with a concession. Though the Law was no substitute for the promise, it yet directly led up to it.

Given life.—This is practically equivalent to “justified,” or “made righteous.” He who is justified has life—both true spiritual life in the present and eternal life in the future. That the Law could not justify had been shown in Galatians 3:11 and in Romans 3:20.

On verses 21-24:

If the Law was thus inferior to the promise, does it therefore follow that it is contrary to it? By no means. The Law could not indeed give life; it could not justify, or place in a state of righteousness. Its real result was rather to place all men in a state of sin. But by so doing it prepared the way for the fulfilment of the promise in all who put faith in Christ. The Law was a close and strict, yet salutary, discipline to make us fit for faith in Christ.