John Gills Exposition of the Bible Commentary

Verse 3 (Galatians 5:3)

For I testify again to every man ,.... This is the form of an oath, a calling God to witness, swearing by the living God, and declaring as in his presence to every man, whether Jew or Gentile, whoever he be:

that is circumcised ; in order to obtain salvation, and as necessary to it:

that he is a debtor to do the whole law ; and this it is that made circumcision an insupportable yoke, for that itself might be bore, and was bore by children of eight days old; but the fulfilling of the whole law cannot be done by any man; and yet everyone that is circumcised, in order to procure righteousness and life, is bound to keep the whole law; because the law is only his righteousness, when he observes all that is required in it, and as the Lord has commanded; if he does not, he is pronounced accursed: and this proves what was before said, that Christ is of no profit to such persons; because they reject him and his righteousness, and, as much as in them lie, make void his obedience, sufferings, and death: hence the same thing is repeated, though not in the same words, in the next verse.

- John Gills Exposition of the Bible Commentary