You shall not take revenge and not bear a grudge against the members of your people; you shall love your neighbor as yourself. I am Hashem. (VaYikra 19:18)
1. The challenge of loving one’s neighbor to the standard proscribed by the Torah
These passages instruct us that we may not take revenge or bear a grudge against another and that we are required to love one another. The pasuk delineates two prohibited forms of behavior: taking revenge and bearing a grudge. What is the difference between these two forms of behavior? Our Sages explain that taking revenge is more direct. It involves acting towards a person in the same hurtful manner that one has been treated by this person. For example: I ask to borrow from a friend his pen and he refuses. The next day this friend needs to borrow a pen from me. I remind the friend of his response to my request the previous day and refuse the pen. This is taking revenge. Bearing a grudge is more passive. In the above example, if I lend the pen but point out to the friend that I am not behaving as he behaved to me, this is bearing a grudge. Bearing a grudge is prohibited because it too is a form of hatred. As the second portion of the passage teaches, we are to love one another.
The pasuk’s directive to love one another is remarkable in two respects. First, the passage instructs us to love our neighbor as we love ourselves. This is a wonderful goal. However, our Sages noted that it does not seem to be a very realistic objective. Certainly, we should try to overcome the pettiness and self-centeredness that often interfere with our empathy, compassion, and love for others. But a directive to love another person to the degree one loves oneself seems to require the impossible.
Second, our Sages did not regard this directive as a mere ethical exhortation – an appeal to act with love towards others. The Sages regarded this directive as an absolute commandment. It is included in the Torah’s 613 mitzvot. This compounds the first difficulty. Torah is not only establishing an impossible standard of behavior, it is commanding us to achieve the impossible!
2. Loving one’s neighbor focuses on actions not feelings
Various commentaries suggest different answers to these problems. Rabbaynu Avraham ibn Ezra explains that the meaning of the instruction is that we should love those things that benefit our friends as we love those things that benefit ourselves. In other words, the Torah is not suggesting that we actually feel for our friends the same love we feel for ourselves. This would not be realistic. The Torah is establishing a standard of behavior. We must be as scrupulous in caring for the needs of our neighbor as we are in caring for our own needs. This remains a high standard, but it does not contradict human nature.
Although Ibn Ezra’s interpretation of the passage is somewhat helpful, it is also somewhat vague. What exactly does the passage require? Does it mean that if I need a new home for myself, I must also provide housing for all homeless individuals?
3. The centrality of the commandment to love one’s neighbor
There is a well-known teaching of Hillel that may explain Ibn Ezra’s position. Hillel explained that a person should not do to another person that which he would not want done to himself. Hillel went on to explain that the remainder of the Torah is merely an elaboration of this principle.
Hillel’s lesson is empirically compelling. Many of society’s problems could be solved if this principle were universally adopted. But Hillel’s contention that this is the essence of the Torah and the rest is merely an elaboration seems to be an overstatement. Perhaps, Hillel did not intend for this last part of his teaching to be taken literally; he was not suggesting that it is okay to deny Hashem’s existence as long as you are nice to people. But if Hillel did not intend for his statement to be understood literally, what was the message he was attempting to communicate?
Sefer HaChinuch suggests that Hillel noted that so many of the mitzvot of the Torah are designed to regulate relations among people. We are not permitted to steal. We cannot overcharge. We are prohibited from engaging in various deceptive business practices. We must return lost objects. All of the commandments are designed to foster and encourage harmony among the individual members of society. Hillel recognized that all of these laws are amplifications of a single theme. They attempt to create a society in which all members have equal rights to fair and compassionate treatment by one another. All of these laws are designed to prevent one member of the group from taking advantage of another. Hillel explained that we each to treat our friends as we wish to be treated, all of these laws would be superfluous.,
Sefer HaChinuch’s comments provide an explanation of Ibn Ezra’s position. We are not expected to be as solicitous of the needs of others as we are of our own needs. However, we are expected to regard his needs as being as serious and real as our own. Therefore, we need not provide shelter for the homeless before building a home for ourselves. We have every right to care for our own needs first. But we cannot dismiss other’s needs as insignificant. When the poor require our assistance, we cannot be dismissive. Certainly, I cannot place my rights before those of another person. I must respect those rights as I would expect my own to be respected.
We can only recognize the full implication of this commandment if we acknowledge that this is not our usual attitude. If we are honest, we will admit that although we do not dismiss our friend’s needs, we tend to see them as somewhat less compelling than our own. If we honestly review our interactions with others, we will be able to identify behaviors that place our needs above others. The Torah is commanding us to identify these behaviors and correct them.
In short, according to Sefer HaChinuch, we are required to respect other’s rights and needs as we do our own. This attitude fosters harmony within a group or society. In a society in which the attitude is not present, there will be friction and discord.
4. We are all fingers of a single hand
Rav Naftali Tzvi Berlin Zt”l – Netziv – offers an alternative understanding of the objective of this commandment. He begins by quoting a teaching from the Jerusalem Talmud. The Talmud observes that we are forbidden from taking vengeance. The Talmud explains that vengeance is absurd. This is illustrated with an analogy. A person is cutting meat; his hand holding the knife slips and he cuts his other hand. Would the person then take punish the hand that slipped by cutting it as well? The Talmud concludes by explaining that this is the message of our passage. We may not take vengeance because we must love one another. We are all similar to the fingers of a single hand, or limbs of a single body. If we take vengeance upon another person – even to redress a wrong – we are cutting one of our own limbs. , 
It seems that Netziv is explaining that the mitzvah to love one another is not merely designed to serve a practical purpose. It is not designed to assure order and harmony in society. It has a higher purpose. It is designed to reorient our perspective upon ourselves. We are commanded to refrain from vengeance and to love one another in order to foster within ourselves a healthy and truthful perspective. We must recognize that we are members of a group and nation. This does not mean the individual is not important, or that a person’s sense of individual significance is improper. But our sense of our own individual importance cannot overwhelm our realization and acknowledgement that we are also part of Bnai Yisrael.
In summary: According to Sefer HaChinuch, the mitzvah to love one another is essentially a social contract. It is designed to foster harmony. According to Netziv, the commandment is designed to nurture within each person a healthy and truthful perspective on himself. Each of us must be able to see ourselves as a member of a group and nation.
 Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer VaYikra 19:18.
 Rabbaynu Avraham ibn Ezra, Commentary on Sefer VaYikra 19:18.
 Mesechet Shabbat 31a.
 Rav Aharon HaLeyve, Sefer HaChinuch, Mitzvah 243.
 If the principle of loving one’s neighbor as oneself finds its expression in the many commandments that regulate our interactions, then the commandment seems to be superfluous! Why is such a commandment required if its practical applications are legislated by other commandments? Apparently, this commandment provides guidance in situations that are not directly included in the specific derivative commandments. In other words, the specific commandments regulating our interactions cannot address ever particular circumstance that may arise. Therefore, the Torah expresses the underlying principle – to love one’s neighbor as oneself – as a commandment. This general commandment provides us with direction and guidance in instances not specifically addressed by the derivative commandments.
 Talmud Yerushalmi, Mesechet Nedarim 9:4.
 Rav Naftali Tzvi Yehuda Berlin (Netziv), Commentary Hamek Davar on Sefer VaYikra 19:18.