“You may not take revenge nor may you bear a grudge against the people of your nation!” (Vayikra 19:18)
It is a negative commandment, that one must not take revenge. That means to say that we have been forbidden to take revenge against a Jew. If a Jew did bad to or hurt a fellow Jew in any way, (when the custom of most people in the world is that they will leave no stone unturned until they find the person who has done the bad thing to them and pay him back for the evil which he did or hurt him in the same way that he had hurt them,) the Torah has withheld us from paying back in any way when the verse says “You may not take revenge!”. If, for example, Reuven says to Shimon, “Please lend me your sickle.”, and Shimon did not lend it, and when the next day Shimon asks Reuven “Please lend me your axe.”, Reuven says, “I will not lend you my axe in the same way that you did not lend me your sickle!”, Reuven has transgressed the commandment of “You may not take revenge!”.
The root of the commandment is that a person must know and take to heart that everything which happens to him, whether good or bad and everything in between, comes from Hashem Yisbarach. No other person is allowed to do anything to him without the will of Hashem. Therefore, when a person hurts him or makes him feel bad, one should know that it is one’s own sins which have caused this to happen, and Hashem has decreed that he should receive this. He should therefore not think in his mind how to take revenge against his friend, for his friend is not the cause of the evil, rather the sin is the cause. Another wonderful effect of this commandment is that it quietens quarrels and removes bad feelings from people’s hearts, and if there is peace between people, Hashem will also act with peace to them.
This commandment applies in all places and at all times, to men and women. One who decides to hate his friend (for a bad thing which he did) until such time as he manages to take revenge has transgressed this prohibition, and it is a great evil for it causes much damage.
It is a negative commandment not to bear a grudge (literally not to guard). This means that we are forbidden to keep in our hearts that which another member of Klal Yisrael has harmed us. This remains true even if we have decided not to pursue any form of retribution for his deeds. We are forbidden even to keep it in our hearts and about this the Torah says “Do not bear a grudge!”. An example of this prohibition is if Reuven says to Shimon “Please lend me your sickle.”, and Shimon refuses to lend it, and the following day Shimon says to Reuven “Please lend me your axe.”, and Reuven answers “Here is my axe. I am not like you who did not lend me your sickle.” By so answering he has transgressed this prohibition.
The other facts of this commandment are identical to that of the preceding commandment (Do not take revenge!).