St. John Chrysostom: Homily 16 on Matt. 5-6: The new and the old law

After having threatened prevaricators and promised great rewards for the righteous, after having shown that it is just to exact from us something beyond the old measure, Christ begins to legislate, not absolutely, but by way of comparison with the ancient ordinances; he shows thus that there is no contradiction, but, on the contrary, perfect harmony, between the law which he instituted and that which preceded it; besides, it is normal and fitting that the one should complete the other. And that this may be made quite clear, listen to the words of the Legislator: You have heard that it was said to the men of old, Thou shalt do no murder. . . But I tell you that any man who is angry with his brother must answer for it before the court of justice. Not to be angry and not to kill, are these contrary to one another or rather is not one the complement or perfection of the other? Clearly the one is the fulfilling of the other, and hence is shown the superiority of the new law. He who is not stirred up to anger, will all the more refrain from murder; when one controls one's heart one will better control one's hand. Wrath is the root of murder; destroy the root and you certainly destroy the branches, nay further, they will not shoot at all. It follows from that that Christ imposed these precepts not to abolish the law but to render its observance surer and more easy.

Nevertheless, thinking of the old law, which ordained an eye for an eye and a tooth for a tooth, some cry out: "How could he be good who speaks so?" How shall we meet this difficulty? By saying that there precisely shines forth the' love of God for man. The law, indeed, far from encouraging us to put out one another's eyes, has for its aim to hinder us, by the fear of meriting the same treatment ourselves. Thus God threatened the Ninevites with extinction' not in order to carry out his threat, (for in that case, he would have done better to be silent), but that by fear he might make them better and so disarm his anger; so likewise, he threatens a like suffering to those who wantonly tear out the eyes of their brethren, that if their conscience does not refrain them, fear may prevent them from this act of cruelty.

For our part, we see but one and the same Legislator in the two Testaments, disposing all things in perfect order, and pouting each enactment in harmony with the deference of the two times. Thus then, neither are the first commandments cruel, nor are the second overwhelming and burdensome: all come from the one and the same goodness.