Leviticus chapters 17-26 is known as the Holiness Code. It contains mainly commandments whose goals are to infuse holiness into the People of Israel, just as God is holy. These commandments, particularly in chapter 19, for the first time make it clear that holiness is not just a property of the relationship between humans and God, but also between human beings and other human beings. The equal weight of these two relationships comes together literally in 19:3 "You shall each revere his mother and his father, and keep My sabbaths."
Chapter 19, vv. 1-18, are below in English and Hebrew. They culminate, in v. 18, with "And you shall love your fellow man as yourself." (Translation by Robert Alter. Biblical text translation below is NewJPS.) As Alter writes in his translation with commentary The Five Books of Moses (W.W. Norton & Co., 2004) on this chapter, "When the sundry injunctions here conclude with the reiterated formula 'I am the Lord,' the implication is 'I am the Lord your God Who is holy." (p. 625)
[See the bold print in the text below.]
The biblical text is in the boxes and below that are various commentaries from the Talmud, midrash, medieval and modern rabbinic commentators, legal codes, and more.
Rashi on Leviticus 19:18 (11th c. France)
You shall not take vengeance or bear a grudge. Suppose someone asks his friend, "Lend me your knife," and the other man turns him down. The next day the second man says, "Lend me your shovel." If the first man says, "I won't lend it to you, just as you wouldn't lend your knife to me" - that is "vengeance." And what is bearing a grudge? As follows: The first man says, "Lend me your shovel," and the other one refuses. Next day, the second man says, "Lend me your knife." The first man replies, "Here it is. I am not going to refuse to lend it to you, as you did to me." That is "bearing a grudge." The Hebrew verb refers to holding on to something or retaining it. When someone bears a grudge, he holds on to his enmity in his heart even if he does not take vengeance.
Love your fellow as yourself. It is forbidden to do to others what you would not want done to yourself. Rabbi Akiva said: "This is a great principle of the Torah." (Sifra, Kedoshim, Chapter 4 12; Talmud Yerushalmi Nedarim 9:3.)
Sforno on Leviticus 19:18:1 (15th-16th c. Italy)
There follows a general, all inclusive rule to be observed in relations towards one’s fellow, phrased as ואהבת לרעך כמוך, telling us to apply the same yardstick to our concern for our fellow that we would want applied to ourselves if we were in his shoes in similar situations.
Shabbat 31a (Talmud)
There was another incident involving one gentile who came before Shammai and said to Shammai: Convert me on condition that you teach me the entire Torah while I am standing on one foot. Shammai pushed him away with the builder’s cubit in his hand. This was a common measuring stick and Shammai was a builder by trade. The same gentile came before Hillel. He converted him and said to him: That which is hateful to you do not do to another; that is the entire Torah, and the rest is its interpretation. Go study.
Hizkuni, Leviticus 19:18:5 (13th c. France)
ואהבת לרעך כמוך, “if you (and everyone else) will practice this virtue you will contribute to peaceful relations between man and his fellow.” The prefix letter ל before the word רעך, “your fellowman,” is superfluous. An alternate interpretation: the Torah was careful not to write ואהבת רעך כמוך “love your fellowman as you love yourself,” as this is something impossible for human beings to do. It is however, possible to love things that belong to your fellow human being as much as you love the things that are your own. You are to put yourself mentally into the position of your fellow human being, and therefore not to do anything to him that you would not have others do to you. By the same token you should love as much to do favours for him as you would have others do favours for you. The same interpretation also applies to verse 34 in our chapter where we are asked to love the convert to Judaism כמוך, “just like yourself.”
Like the native among you shall be the sojourner who sojourns with you, and you shall love him like yourself, for you were sojourners in the land of Egypt. I am the Lord your God. [Alter translation]
The word "ger" גר, in Hebrew, is translated as convert, proselyte, stranger, or sojourner.
Sifra, Kedoshim, Chapter 8 4 (Midrash on Leviticus)
Lev. 19:34: "... the stranger that lives among you. And you shall love him as yourself." Just as it is written of Jews (Vayikra 19:18) "and you shall love your fellow as yourself," so is it written of proselytes "and you shall love him as yourself." "for you were strangers in the land of Egypt": Know the soul of the strangers, for you yourselves were strangers in the land of Egypt."
Mishneh Torah, Human Dispositions 6:3 (Legal Code)
It is mandatory upon every man to love each and every one of Israel even as he loves his own self, for it is said: "But thou shalt love thy neighbor as thyself" (Lev. 19.19.). One is therefore, obliged to speak in praise of his neighbor, and to be considerate of his money, even as he is considerate of his own money, or desires to preserve his own honor. "But whosoever glorifies himself in disgracing his neighbor has no share in the world to come" (Yerushalmi, Hegigah. 2.1).
Mishneh Torah, Positive Mitzvot 206 (Legal Code)
To love all human beings, who are of the covenant, as it is said, “Thou shalt love thy neighbour as thyself” (Lev. 19:18).
This interpretation is that this positive commandment refers only to Jews, translating the Hebrew word re'a רע as fellow or neighbor very specifically. See below for the inclusion of proselytes/strangers.
See Nehama Leibowitz and Sifra Kedoshim (12 and 13) for proof that this commandment refers to all human beings.
Mishnah Torah, Human Dispositions 6:4 (Legal Code)
The love for the proselyte, who came and embraced the protection beneath the wings of the Shekinah, rests upon two mandatory commandments, one because he is included in the commandment concerning a neighbor, and the other because he is a stranger, and the Torah charged us, saying: "Love ye therefore the stranger" (Deut. 10.19.). He commanded on the love for the stranger as He commanded concerning the love for Himself, saying: "And thou shalt love the Lord thy God" (Ibid. 6.5.). The Holy One, blessed is He! loves the strangers Himself, even as it is said: "And (He) loveth the stranger" (Ibid. 10.18).
Nehama Leibowitz, 20th c. Biblical scholar
Leibowitz writes that the Hebrew word re'a is a neutral and comprehensive term - fellow. Its identification with an "Israelite" is conclusively refuted, she says, by the word's use in Exodus 11:2, "Let every man ask of רעהו his neighbor and every woman of רעותה her neighbor, jewels of silver and jewels of gold..." where it clearly refers to the Egyptians.
[This is when the Israelites are preparing to flee Egypt, the day before the final plague.]
From New Studies in VaYikra (Leviticus), WZO, 1995, pp. 366-367.
Sifra, Kedoshim, Chapter 4 12 (Midrash on Leviticus)
This is the midrash that Rashi quotes in source 2 above when he cites Rabbi Akiva.
BUT, Rashi does not mention that Ben Azzai argues that there is a more important principle, which is found in Genesis 5:1.
12)...R. Akiva says: This is an all-embracing principle in the Torah. Ben Azzai says: (Bereshith 5:1) "This is the numeration of the generations of Adam" — This is an even greater principle.
This is the text of Gen. 5:1:
This is the book of the generations of Adam,
on the day that God created the human,
in the image of God He created him.
Ben Azzai is implying that all human beings are created equal and in the image of God. That is the reason that we must treat each human being as holy, Israelite or not-Israelite. It also answers the question, How can we be commanded to love, which is a feeling? As Art Green writes in his lovely little book Judaism's 10 Best Ideas: A Brief Guide for Seekers, (chapter 2, "Tzelem Elohim - Creation in God's Image"): "Ben Azzai offers a principle to which there can be no exceptions, since it goes right back to Adam and Eve. Every human being is created in the image of God. Love them or not, neighbor or enemy, you must treat them all as you would treat God's image."
Sefer HaHinukh 243:1 ("Book of Education," commentary on the commandments in the Torah, 13th c. Spain
The commandment of love of Israel: To love [with] love of the soul each one of Israel - meaning to say that we have compassion for an Israelite and for his money, [just] like a person has compassion for himself and for his [own] money; as it stated (Leviticus 19:18), "you shall love your neighbor as yourself." And they, may their memory be blessed, said (Shabbat 31a), "What is hateful to you, do not do to your fellow." And they said in Sifra, Kedoshim, Chapter 4:12, "Rabbi Akiva said, 'This is a great principle in the Torah'" - meaning to say that many commandments are dependent upon it. As one that loves his fellow like himself will not steal his money, have adultery with his wife, cheat his money from him nor hurt him from any angle. And so [too,] are there several other commandments dependent on this - the thing is well-known [revealed] to all who have intellect.
Sefer HaHinukh 431:1 (see above)
The commandment of loving the strangers (converts): That we were commanded to love the converts, meaning to say that we be careful not to cause them pain in any thing, but [rather to] do them good and grant them kindness according to what is proper and is possible. And converts are anyone who connects with us from the other nations, that leaves his religion and enters into our religion. And about them is it stated (Deuteronomy 10:19), "And you shall love the stranger, etc." And even though the commandment (Sefer HaChinukh 243) about the Israelite includes him, as it is stated about him (Leviticus 19:18), "and you shall love your neighbor as yourself" - since behold, a righteous convert is included in "your neighbor" - God added for us a specific commandment about his love. And so too is the thing in the prevention against cheating him. As even though he was included in "A man shall not wrong his countryman" (Leviticus 25:17, Sefer HaChinukh 338), Scripture added a specific prevention about him in its stating, "You shall not wrong a stranger" (Exodus 22:20, Sefer HaChinukh 23). And they said in the Gemara (Bava Metzia 59b) that one who wrongs the convert transgresses because of "[A man] shall not wrong" and because of "You shall not wrong a stranger." And so too [with this], he nullifies the commandment of "and you shall love your neighbor" and the commandment of "And you shall love the stranger."
Contemporary Halakhic Problems, Vol II, Part I, Chapter III, Medical Questions 6
An obligation requiring the physician to render assistance in nonlife-threatening situations may be established on the basis of other sources. Ramban, in his Torat ha-Adam, finds that an obligation on the part of the physician to heal is inherent in the commandment "And you shall love your neighbor as yourself" (Leviticus 19:18). As a specific instance of the general obligation to manifest love and concern for one's neighbor, the obligation to heal encompasses not only situations posing a threat to life or limb, or demanding restoration of impaired health, but also situations of lesser gravity warranting medical attention for relief of pain and promotion of well-being.
Gray Matter III, Estate Planning, Disinheritance 12 (contemporary halakhic questions)
In all cases, it must be strongly emphasized that a will must not be used as a tool for revenge. The Torah explicitly forbids taking revenge (Vayikra 19:18), and this prohibition applies no less on the deathbed.
From "Of Love and Hate" by Rabbi Lord Jonathan Sacks, May 12, 2016 (Parshah Kedoshim)
On vv. 19:17-18:
(17) Do not hate your brother in your heart. You must surely admonish your neighbour and not bear sin because of him. (18) Do not take revenge or bear a grudge against the children of your people. Love your neighbour as yourself. I am God.
"The inner logic of the two verses in our Torah portion is therefore this: “Love your neighbor as yourself. But not all neighbors are loveable. There are those who, out of envy or malice, have done you harm. I do not therefore command you to live as if you were angels, without any of the emotions natural to human beings. I do however forbid you to hate. That is why, when someone does you wrong, you must confront the wrongdoer. You must tell him of your feelings of hurt and distress. It may be that you completely misunderstood his intentions. Or it may be that he genuinely meant to do you harm, but now, faced with the reality of the injury he has done you, he may sincerely repent of what he did. If, however, you fail to talk it through, there is a real possibility that you will bear a grudge and in the fullness of time, come to take revenge..
"What is so impressive about the Torah is that it both articulates the highest of high ideals, and at the same time speaks to us as human beings. If we were angels it would be easy to love one another. But we are not. An ethic that commands us to love our enemies, without any hint as to how we are to achieve this, is simply unliveable. Instead, the Torah sets out a realistic programme. By being honest with one another, talking things through, we may be able to achieve reconciliation – not always, to be sure, but often. How much distress and even bloodshed might be spared if humanity heeded this simple command."