Salvation must be by grace. If man is lost by sin, how can he be saved except through the grace of God? If he has sinned, he is condemned; and how can he, of himself, reverse that condemnation?
Suppose that he should keep the law for the rest of his life, he will then only have done what he was always bound to have done, and he will still be an unprofitable servant.
What is to become of the past? How can old sins be blotted out? How can the old ruin be retrieved?
According to Scripture, salvation can only be through the free favour of God, “For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.” (Ephesians 2:8-9)