Jesus is the new Moses, and just as Moses went up on Mount Sinai to receive the law from God, Jesus goes up on the mountain to receive from the Father and then transmit to God's people the law of the kingdom. This new law of the kingdom doesn't abolish the law of Moses, it amplifies it. And so Jesus says, "you have heard it said (in the law), but I say to you…" and then he raises the standard given by the law by the power of ten.