“And you shall love your friend as you love yourself!” (Vayikra 19:18)
It is a positive commandment to love each and every member of the Jewish nation with a love which comes from the soul. This means to say that we should have concern for a Jew and his money in the same way that a person has concern for himself and his own money, as it says “And you shall love your friend as you love yourself!”. Chazal paraphrased this by saying “What is hateful to you, do not do to your friend!”, and Rabbi Akiva said that this is a great rule in the Torah, which means that many of the Torah’s commandment are dependent on this rule, for one who genuinely loves his friend will not steal from him or trick him or hurt him financially or physically; he will not trespass on his property, nor damage him in any way. There are similarly many other commandments which depend on this as any sensible man can see.
The root of this commandment is well-known, for in the way that one interacts with one’s friend, so too one’s friend will reciprocate, and there will be peace between the creations.
The laws of this commandment are included in the main commandment, for the rule is that one must conduct oneself in one’s dealings with one’s friend in exactly the same way that he conducts himself with himself, in looking after his money and avoiding all damages. If he must talk about his friend, he should only sing his praises, worry about his honor, and definitely not rejoice in his embarrassment, as Chazal said, “One who glorifies in his friend’s downfall has no portion in the world to come!”. One who deals with his friends with love, peace and friendship, who searches their benefit, and is happy with their doing well, is referred to in the verse which says, “Yisrael which I can glorify myself with you!”.
This commandment applies in all places and at all times.