43 “You have heard that it was said, ‘Love your neighbor’ and ‘hate your enemy.’ 44 But I say to you, love your enemy and pray for those who persecute you, 45 so that you may be like your Father in heaven, since he causes the sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. 46 For if you love those who love you, what reward do you have? Even the tax collectors do the same, don’t they? 47 And if you only greet your brothers, what more do you do? Even the Gentiles do the same, don’t they? 48 So then, be perfect, as your heavenly Father is perfect.
Gittin 36bBabylonian Talmud
The Gemara continues discussing the meaning of the word ulbena. The Sages taught: Those who are insulted [ne’elavin] but do not insult others, who hear their shame but do not respond, who act out of love and are joyful in their suffering, about them the verse states: “And they that love Him are as the sun going forth in its might” (Judges 5:31).
Notes and References
"... The Rabbis also praised restraint from seeking retribution (Babylonian Talmud Shabbat 88b; Yoma 23a; Gittin 36b). But the first statement comes from a client king of the oppressors who would like nothing better than to keep the people docile. The second comes from one who has the power to sue others for injury in courts of law. The last comes from those who had suffered enough from two ruinous revolts against Rome ... Loving Enemies (5:43-48). It was not uncommon in the ancient world for a farmer to pray to the gods for the protection of his own animal and for the animal of his rival to break its leg. The Hebrew Scriptures, however, enjoin loving the neighbor. The neighbor is carefully defined as the fellow Israelite, although it is also extended to the resident alien (Leviticus 19:18, 33-34; see Deuteronomy 10:18-19). Nowhere does the Scripture explicitly say that one is to hate one’s enemy, although it might be inferred from some passages ..."
Garland, David E. Reading Matthew: A Literary and Theological Commentary (pp. 73-76) Smyth & Helwys, 2001