Romans 5:20

The law entered; a written revelation of the will of God was given and embodied in the moral and ceremonial law of the Old Testament.

That the offence might abound; as men, after the giving of the written law, had more commands and obligations which they knowingly violated, the number and guilt of their sins was greatly increased. Thus the law, through their opposition to it, and their voluntary disobedience of it, aggravated their condemnation; and was adapted to make them feel that if they were ever saved, it must be by grace, and thus prepare them to believe on Christ. Galatians 3:24.

Grace did much more abound; it triumphed over all obstacles, and saved those who believed in Christ, notwithstanding their greatly multiplied and aggravated transgressions.