Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 305
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 305, with English translation by Maimonides (Rambam).
שלא לנטור, שנאמר "לא תיטור" (ויקרא יט,יח).
Not to bear a grudge, as [Leviticus, ibid.] states: "Do not bear a grudge."