"Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them."
Matthew 5:17To the Jews, what was lacking about the commandments, that it needed completing or fulfilling? The big 10, or the 613 - they were what they were, and you had to obey them in order to curry favor with God. Right?
But Jesus proceeds to paint a picture through the rest of the chapter that it is impossible to keep the commandments. There is no one who has not committed murder by holding their brother in contempt. There is no one who has not looked lustfully at another. Etc. etc.
So what was he getting at? That we try harder to be nice? A good idea. Good luck with that. Have fun with that. Indeed, he paints a fairly hopeless picture. Jesus basically says, "When you fail get back to Me and let Me know how that worked out for you."
But the message of hope is that He is the completion of the law. He doesn't lay it out how, just yet. But He does say that He is the completion. The fulfillment. The way out of this place of bondage to hopelessly falling short of perfect obedience.
Continue, then, in following Him until the rest of the story is revealed. This is, after all the way He walks with us as we follow Him; remain in with the One who remains with us through the dirtiness of our living. Because in the end He reveals that there was hope from the beginning.