Ibn Ezra on Leviticus 19:18:3

לא תקם ולא תטר. מפורש בדברי חז״ל: THOU SHALT NOT TAKE VENGEANCE, NOR BEAR ANY GRUDGE. This is explained in the words of our rabbis of blessed memory.⁶⁵See Rashi on this verse. “If one says to another, Lend me your sickle, and he replies, No. The next day the latter says to the former, Lend me your hatchet, and he replies, I am not going to lend it to you, just as you refused to lend me your sickle—this is taking vengeance…If one says to another, Lend me your sickle, and he replies, No! and the next day the latter says to the former, Lend me your hatchet, and he replies, Here it is; I am not like you, because you would not lend me—this is called bearing a grudge.” See also Yoma 23a.

ואהבת לרעך. על דעת רבים שהלמ״ד נוסף כלמ״ד לאבנר ועל דעתי שהוא כמשמעו שיאהב הטוב לחברו כמו לנפשו: BUT THOU SHALT LOVE THY NEIGHBOR. Many are of the opinion that the lamed of le-re’akha⁶⁶Le-re’akha literally means to thy neighbor. (thy neighbor) is superfluous.⁶⁷If we take le-re’akha literally, then our verse reads, but thou shalt love to thy neighbor as thyself. This does not appears to make sense. Hence this interpretation means that we should ignore the lamed prefixed to re’akha and interpret our verse as reading, but thou shalt love thy neighbor as thyself. It is like the lamed of le-avner (Abner) (II Sam. 3:30).⁶⁸Le-avner is to be interpreted as if written avner. I believe that le-re’akha is to be taken literally.⁶⁹That is, the lamed of le-re’akha (thy neighbor) is not superfluous. Its meaning is that one should love that which is good for one’s neighbor as he does for himself.⁷⁰I. E. interprets the lamed of le-re’akha as meaning “for.” He interprets our verse as follows: You shall love for your neighbor what you love for yourself (Krinsky). Weiser claims that I.E. interprets the lamed of le-re’akha as meaning “of.” He interprets our verse as follows: You shall love of your neighbor’s welfare as you love your own welfare.