Grace is what God may be free to do, and indeed what he does, accordingly, for the lost after Jesus has died on behalf of them. It is thus apparent that God's grace is to be distinguished from his mercy and love. Had God been therefore been able to save one soul on the ground of his sovereign mercy alone, He could have saved every person on that basis, and the death of Christ would not have been a necessity. Since God is holy and righteous and sin is a complete offense to Him, His love or His mercy cannot operate in grace until there was provided a sufficient satisfaction for sin. This satisfaction makes possible the exercise of God's grace.
Grace thus rules out all human merit.
It requires only faith in the saving act.