Behold, I Paul. — The strong personality of the Apostle asserts itself; instead of going into an elaborate proof, he speaks with dogmatic authority, as though his bare word were enough.
Shall profit you nothing. — ”Profit,” i.e., in the way of justification, as producing that state of righteousness in the sight of God by virtue of which the believer is released from wrath and received into the divine favour. The Apostle says that if this state of justification is sought through circumcision, it cannot be sought through Christ at the same time.