The Apostle Paul
Galatians 2:21ESV·traditional attribution

I do not nullify the grace of God, for if righteousness were through the law, then Christ died for no purpose.

John Calvin Reformed @genevareformer

21. I do not reject. There is great emphasis in this expression; for how dreadful is the ingratitude manifested in despising the grace of God, so invaluable in itself, and obtained at such a price! Yet this heinous offense is charged against the false apostles, who were not satisfied with having Christ alone, but introduced some other aids towards obtaining salvation.

Matthew Henry Presbyterian @wholebiblehenry

I. From the account which Paul gives of what passed between him and the other apostles at Jerusalem, the Galatians might easily discern both the falseness of what his enemies had insinuated against him and their own folly and weakness in departing from that gospel which he had preached to them.

Commenting on Galatians 2:11-21

John Gill Reformed Baptist @doctorgill

I do not frustrate the grace of God,.... Or "cast it away", as the Vulgate Latin version reads it; or "deny it", as the Syriac and Arabic; or "despise, reject, and make it void", as other versions; meaning either the grace of the Son of God in giving himself for him, just mentioned by him; or the particular doctrine of grace, justification, he is speaking...