Galatians 5:2

If ye be circumcised - By circumcision you take on you the whole obligation of the Jewish law, and consequently profess to seek salvation by means of its observances; and therefore Christ can profit you nothing; for, by seeking justification by the works of the law, you renounce justification by faith in Christ.

Behold, I Paul say unto you - I, who at first preached the gospel to you; I, too, who have been circumcised, and who was formerly a strenuous assertor of the necessity of observing the laws of Moses; and I, too, who am charged (see Galatians 5:11) with still preaching the necessity of circumcision, now solemnly say to you, that if you are circumcised with a view to being justified by that in whole or in part, it amounts to a rejection of the doctrine of justification by Christ, and an entire apostacy from him. He is to be "a whole Saviour." No one is to share with him in the honor of saving people; and no rite, no custom, no observance of law, is to divide the honor with his death. The design of Paul is to give them the most solemn assurance on this point; and by his own authority and experience to guard them from the danger, and to put the matter to rest.

That if ye be circumcised - This must be understood with reference to the subject under consideration. If you are circumcised with such a view as is maintained by the false teachers that have come among you; that is, with an idea that it is necessary in order to your justification. He evidently did not mean that if any of them had been circumcised before their conversion to Christianity; nor could he mean to say, that circumcision in all cases amounted to a rejection of Christianity, for he had himself procured the circumcision of Timothy, Acts 16:3. If it was done, as it was then, for prudential considerations, and with a wish not necessarily to irritate the Jews, and to give one a more ready access to them, it was not to be regarded as wrong. But if, as the false teachers in Galatia claimed, as a thing essential to salvation, as indispensable to justification and acceptance with God, then the matter assumed a different aspect; and then it became in fact a renouncing of Christ as himself sufficient to save us. So with anything else. Rites and ceremonies in religion may be in themselves well enough, if they are held to be matters not essential; but the moment they are regarded as vital and essential, that moment they begin to infringe on the doctrine of justification by faith alone, and that moment they are to be rejected; and it is because of the danger that this will be the case, that they are to be used sparingly in the Christian church. Who does not know the danger of depending upon prayers, and alms, and the sacraments, and extreme unction, and penance, and empty forms for salvation? And who does not know how much in the papal communion the great doctrine of justification has been obscured by numberless such rites and forms?

Christ shall profit you nothing - Will be of no advantage to you. Your dependence on circumcision, in these circumstances, will in fact amount to a rejection of the Saviour, and of the doctrine of justification by him.

5:2 If ye be circumcised - And seek to be justified thereby.Christ - The Christian institution. Will profit you nothing - For you hereby disclaim Christ, and all the blessings which are through faith in him.