John Calvin Commentary James 2:23

"and the scripture was fulfilled which saith, And Abraham believed God, and it was reckoned unto him for righteousness; and he was called the friend of God." — James 2:23 (ASV)

And the Scripture was fulfilled. Those who seek to prove from this passage of James that the works of Abraham were imputed for righteousness must necessarily confess that Scripture is perverted by him; for however they may turn and twist, they can never make the effect its own cause.

The passage is quoted from Moses (Genesis 15:6). The imputation of righteousness that Moses mentions preceded by more than thirty years the work by which they would have Abraham be justified.

Since faith was imputed to Abraham fifteen years before the birth of Isaac, this could not surely have been done through the work of sacrificing him. I consider that all those are bound fast by an indissoluble knot who imagine that righteousness was imputed to Abraham before God because he sacrificed his son Isaac, who was not yet born when the Holy Spirit declared that Abraham was justified. Therefore, it necessarily follows that something subsequent is pointed out here.

Why then does James say that it was fulfilled? It was because he intended to show what sort of faith it was that justified Abraham: namely, that it was not idle or evanescent, but rendered him obedient to God, as we also find in Hebrews 11:8. The conclusion, which is immediately added and depends on this, has no other meaning. A person is not justified by faith alone, that is, by a bare and empty knowledge of God; he is justified by works, that is, his righteousness is known and proved by its fruits.