Leviticus 19:18

Hence it clearly appears that God had a further object than that men should not kill each other, for He not only restrains their hands, but requires their hearts to be pure from all hatred. For, since the desire of vengeance is the fountain and cause of enmities, it follows that under the word kill is condensed whatever is opposed to brotherly love. And this is confirmed by the antithesis, that none should hate his brother, but rather love him as himself. We need, then, seek for no other expositor of the Commandment but God Himself, who pronounces those to be guilty of murder who are affected with any malevolence, and not only those who, when offended, desire to return evil for evil, but those who do not sincerely love their neighbors, even when with justice they deem them to be their enemies. Wherefore, in order that God may absolve us from spiritual murder, let us learn to purify our hearts from all desire of vengeance, and, laying aside hatred, to cultivate fraternal affection with all men.

Although the latter part of the verse embraces the sum of the whole Second Table, yet, because love is contrasted with vengeance, I have not thought fit to separate things which are so properly connected with each other, especially when one depends on the other. The precept is indeed only given with reference to the children of Abraham, because the crime of vengeance would be more atrocious between those who were bound together by fraternal rights; yet it is not to be doubted but that God generally condemns the vice. In the schools¹ this sentence was grossly corrupted; for, since the rule (as they say) is superior to what is regulated by it. they have invented a preposterous precept, that every one should love himself first, and then his neighbors; of which subject I will treat more fully elsewhere. The word rjn, natar, meaning to guard, when used without any addition, is equivalent to bearing an injury in mind; as we also say in French: "garder une injure."²

¹ Fr., "Les Theologiens de la Papaute." C. refers elsewhere to this scholastic maxim: "Nor is the argument worth a straw, That the thing regulated must always be inferior to the rule. The Lord did not make self-love the rule, as if love towards others was subordinate to it; but whereas, through natural pravity, the feeling of love usually rests on ourselves, He shows that it ought to diffuse itself in another direction -- that is, should be prepared to do good to our neighbor with no less alacrity, ardor, and solicitude, than to ourselves." -- Inst., book 2, 8, Section 54. "Again, when Moses commanded us to love our neighbors as ourselves, he did not intend to put the love of ourselves in the first place, so that a man may first love himself and then love his neighbors: as the sophists of the Sorbonne are wont to cavil, that the rule must always go before what it regulates." -- Harm. of the Evangelists, (C. Society's Trans.,) vol. 3. p. 59.

Leviticus 19:18
18. Thou shalt not avenge, nor bear any grudge against the children of thy people; but thou shalt love thy neighbor as thyself: I am the Lord.	18. Ne ulciscaris te, neque serves odium contra filios populi tui: sed diliges proximum tuum sicut teipsum: ego Jehova.