Galatians 5:3

“For I testify again to every man, etc..] 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…”

“For--Greek, "Yea, more"; "Moreover." I testify . . . to every man--as well as "unto you" (Gal 5:2). that is circumcised--that submits to be circumcised. Such a one became a "proselyte of righteousness." the whole law--impossible for man to keep even in part, much less wholly (Jam 2:10); yet none can be justified by the law, unless he keep it wholly (Gal 3:10).”

“For I testify again - Probably he had stated this when he had preached the gospel to them first, and he now solemnly bears witness to the same thing again. Bloomfield, however, supposes that the word “again” here (πάλιν palin) means, on the other hand, or, “furthermore,” or, as we would say, “and again.” That he is a debtor to do the whole law - He binds himself to obey all the Law of Moses. Circumcision was the distinguishing badge of the Jews, as baptism is of Christians. A man, therefore, who became circumcised became a professor of the Jewish religion, and bound himself to obey all its special laws. This must be understood, of course, with reference to the point under discussion; and…”

“I testify to every man - Every gentile. That is circumcised - He thereby makes himself a debtor - Obliges. Galatians 5:4”

“5:3 Those who seek righteousness through the law must obey every regulation of it (see 2:15-16; cp. Jas 2:10).”

“testify: Deu 8:19, Deu 31:21; Neh 9:29, Neh 9:30, Neh 9:34; Luk 16:28; Act 2:40, Act 20:21; Eph 4:17; Th1 4:6; Jo1 4:14 a debtor: Gal 3:10; Deu 27:26; Mat 23:16, Mat 23:18 \*Gr: Jam 2:10, Jam 2:11 Galatians 5:4”