Romans 4:14-15

If those who are (followers) of the Law are (the true) heirs (of Abraham) then faith (leading to salvation) is of no effect and void, and the promise (of God) nullified. For the Law results in (God’s) wrath (against sin), but where there is no law, there is no violation (of it either).

When reading the Old Testament, it is clear that keeping the law would be a struggle. Without salvation and the guidance of the Holy Spirit, a man quickly loses focus on the law and sins. Through salvation, grace removes the law as a barrier to reaching a connection to God through Jesus.