The 305th prohibition is that we are forbidden from bearing a grudge, even if we don't take revenge. This means we remember the wrongdoing that the person did to us, and mention it to him.

The source of this commandment is G‑d's statement (exalted be He),1 "Do not take revenge nor bear a grudge."

In the words of the Sifra, "How far does the prohibition against bearing a grudge go? If a person requests, 'Lend me your sickle,' and the other won't lend it; and tomorrow [the latter] requests, 'Lend me your ax,' and he answers, 'Here it is — I'm not like you, who wouldn't lend me your sickle.' In this case the Torah says,2 'Do not bear a grudge.'"