Our Lord came to fulfill the law. He changed a lot of things. And His word is pretty much the final word. The religious leaders of the time would not dirty themselves by associating with sinners and publicans. They had a lot of other rules, too, that Jesus said were wrong. In their eyes Jesus did wrong. But Jesus is God and therefore He is the one who decides what is right and what is wrong. They taught as God's laws what were really just men's precepts. People, even today, are forever getting the two mixed up.