It's kind of funny that Jesus had to say early on in the Sermon on the Mount (what Matt. 5-7 is generally called) that he didn't come to abolish the law. The opposite seems to be true. Doesn't it almost seem that he is making the law... worse? Every time he says, "you have heard it said... but I say," he is making the law seem so much more impossible to keep. But that's the point. The law is impossible to keep. The law doesn't redeem us, only God can do that. So when Jesus seems to be making things seem hopeless, he is. Because without him, things are indeed hopeless.