Albert Barnes Commentary Galatians 3:22

"But the scriptures shut up all things under sin, that the promise by faith in Jesus Christ might be given to them that believe." — Galatians 3:22 (ASV)

But the Scripture. This refers to the Old Testament (John 5:39), which contains the law of Moses.

Has concluded all under sin. This means it has shut up (sunekleisen) everyone under the condemnation of sin; that is, it has declared all people, no matter what their rank and external character, to be sinners. Of course, they cannot be justified by that law which declares them to be guilty and condemns them, any more than the law of the land will acquit a murderer and pronounce him innocent while at the same time holding him to be guilty. Regarding the meaning of the expression used here, see Romans 11:32.

Compare Romans 3:9, 19.

That the promise by faith of Jesus Christ, etc. This refers to the promise made in the transaction with Abraham—the promise of justification and life by faith in the Messiah. Here we see one design of the law. Its purpose was to show that people could not be justified by their own works, to hedge up their way regarding justification by their own righteousness, and to show them their need for a better righteousness. The law accomplishes the same purpose now. It shows people that they are guilty, and it does this so that they may be brought under the influence of the pure system of the gospel and become partakers of the promises connected with eternal salvation.

For "promise by faith," see Romans 4:11, 12, 16.