Negative Commandment #81
Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
Second Section – the Negative Commandments
81. It is a negative commandment "do not have hatred in your heart against your friend"
As it states in Vayikra (Leviticus) 19:18, "do not bear a grudge." Having a grudge means keeping hatred in one's heart. An example would be if someone says, "Here I am lending this to you because I am not like you when you refused to lend to me." This is bearing a grudge because it is keeping hatred in one's heart. Rather, a person should lend the item with a full heart, without any hatred in it. He should remove the past event from his heart and not retain it or remember it at all. The two traits [revenge & bearing a grudge] are extremely bad. For everything in this world is like nothing and it is not worth taking revenge or bearing a grudge about them.
This applies in all places and at all times, for men and for women.