Going even further, Jesus perfects the dietary law, so important in Jewish daily life, by revealing its pedagogical meaning through a divine interpretation: "Whatever goes into a man from outside cannot defile him. . . (Thus he declared all foods clean.). . . What comes out of a man is what defiles a man. For from within, out of the heart of man, come evil thoughts. . ." In presenting with divine authority the definitive interpretation of the Law, Jesus found himself confronted by certain teachers of the Law who did not accept his interpretation of the Law, guaranteed though it was by the divine signs that accompanied it. This was the case especially with the sabbath laws, for he recalls, often with rabbinical arguments, that the sabbath rest is not violated by serving God and neighbor, which his own healings did.
-- CCC 582