'Invalidate' in the Bible

I do not ignore or nullify the [gracious gift of the] grace of God [His amazing, unmerited favor], for if righteousness comes through [observing] the Law, then Christ died needlessly. [His suffering and death would have had no purpose whatsoever.]”

What I am saying is this: the Law, which came four hundred and thirty years later, does not invalidate a covenant previously ratified by God, so as to nullify the promise.