NOTES for Lev 19:18
The commandment to love one's neighbor, which many today perceive as exclusively New Testament, in fact existed long before the Savior came into the world. The Book of Leviticus connects love for one's neighbor with the refusal of revenge, and thereby with the New Testament "rule of the other cheek": there too the issue is precisely revenge, the material or moral compensation that one could demand for an insult. In this case, of course, the matter is not a beating, but an insult, a slap in the face.
Jesus connects the "rule of the other cheek" with the norm of the Torah that presupposes recompense according to the principle "eye for eye, tooth for tooth." Such a norm is indeed present in the Torah, and it presupposes precisely revenge. But in that case it turns out that not only in Jesus' words, but in the Torah itself, there are norms contradicting the principle "eye for eye, tooth for tooth." How is this possible? Much becomes clearer if we remember the legal context in which this norm is given. It appears in the text of the Book of Exodus, and it can also be found in Deuteronomy, though there it is only repeated.
The legislation of the Book of Exodus says much about material compensation in the case of intentional or unintentional injury inflicted on one's neighbor: a whole system of fines designed for this case is described there. And in addition to it the rule "eye for eye, tooth for tooth" is given. This is evidently an alternative way of resolving a conflict. Alternative, and very archaic, going back to pre-biblical, pre-Yahwistic customs and norms. These, apparently, had not yet been forgotten in the time when the legislation that entered the Book of Exodus was created.
Blood vengeance and the principle of inflicting proportional harm come from there, from pre-Yahwistic antiquity. The Torah does not prescribe revenge; it only limits it as part of the practice then existing. But the Book of Leviticus, a later book, already requires the renunciation of revenge for the sake of love for one's neighbor. It is no wonder that the Savior requires the same, since revenge is utterly incompatible with the life of the Kingdom. Thus He brings to completion the tendency that had been clearly marked by the Torah already in its earliest forms. And this is understandable: He Himself said that He came not to destroy the Torah, but to reveal it in its fullness. In the fullness of the Kingdom.