Matteo 5:21

The Lord now proceeds to prove His condemning statement by expounding a few of the commandments of the Law according to their full spiritual significance: Ye have heard that it was said by them of old time, Thou shalt not kill: and, Whosoever shall kill, shall be in danger of the judgment.

They were accustomed to hear this in the regular synagogue services, where the reading of the Law was never omitted. It was said both to them of old time, Exodus 20:13; Deuteronomy 5:17; Genesis 9:5-6, and by them of old time, in the precepts delivered by tradition from father to son as well as by the teachers of the people, 2 Chronicles 17:7-9, but the addition, fixing the penalty, was made in the interpretation of the rabbis.

But by this explanation the meaning of "kill" was restricted to actual murder, and the commandment of God became a mere external legal enactment. The end of the transgression was penalized, but the beginning, in desires, in thoughts, in words, was not restrained. "Behold, that is the beautiful holiness of the Pharisees, which can cleanse itself, and remain pious, so long as it does not kill with the hand, though the heart be filled with anger, hatred, and envy, the tongue also with cursing and blaspheming."