23 And the Scripture was fulfilled. They 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 to be its own cause. The passage is quoted from Moses. (Genesis 15:6.) The imputation of righteousness which Moses mentions, preceded more than thirty years the work by which they would have Abraham to have been 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. It hence necessarily follows that something posterior is pointed out here.
Why then does James say that it was fulfilled? Even because he intended to shew what sort of faith that was which justified Abraham; that is, that it was not idle or evanescent, but rendered him obedient to God, as also we find in Hebrews 11:8. The conclusion, which is immediately added, as it depends on this, has no other meaning. Man 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.