Here is the Twitter version of the reason for the Law, and the nullification of it through Jesus Christ:

Wherefore (i.e., for what purpose) then serveth the law?   It was added because of transgressions, till the seed (Christ) should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.” — Galatians 3:19

Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.  But after that faith is come, we are no longer under a schoolmaster.”  — Galatians 3:24,25

Once you get to that second paragraph, the hard work begins…