John Calvin on Galatians 3:18

18. If the inheritance be of the law. His opponents might still reply, that nothing was farther from their intention than to weaken or disannul God’s covenant. To deprive them of every kind of subterfuge, he comes forward with the assertion, that salvation by the law, and salvation by the promise of God, are wholly inconsistent with each other. Who will dare to explain this as applying to ceremonies alone, while Paul comprehends under it whatever interferes with a free promise? Beyond all doubt, he excludes works of every description. “For,” says he to the Romans,

“if they which are of the law be heirs, faith is made void, and the promise made of none effect.” (Romans 4:14.)

Why so? Because salvation would be suspended on the condition of satisfying the law; and so he immediately concludes:

“Therefore it is of faith, that it might be by grace, in order that the promise might be sure to all the seed.” (Romans 4:16.)

Let us carefully remember the reason why, in comparing the promise with the law, the establishment of the one overturns the other. The reason is, that the promise has respect to faith, and the law to works. Faith receives what is freely given, but to works a reward is paid. And he immediately adds, God gave it to Abraham, not by requiring some sort of compensation on his part, but by free promise; for if you view it as conditional, the word gave, (κεχάρισται,) would be utterly inapplicable.

Galatians 3:19-22

19. Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.

19. Quid igitur Lex? transgressionum causa adjuneta fuit, donee veniret semen, cui promissum fuerat, ordinata per angelos in manu mediatoris.

20. Now a mediator is not a mediator of one, but God is one.

20. Porro mediator unius non est; Deus autem unus est.

21. Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.

21. Lexne igitur adversus promissiones Dei? absit; nam si data esset Lex, quae posset vivificare, vere ex Lege esset justitia.

22. But the scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe.

22. Sed conclusit Scriptura omnia sub peccatum, ut promissio ex fide Iesu Christi daretur credentibus.