Negative commandment · Lo Ta’aseh #302 of 613
Not to bear hatred in one's heart
שלא לשנוא בלב
The verse · Vayikra 19:17
לֹא־תִשְׂנָא אֶת־אָחִיךָ בִּלְבָבֶךָ הוֹכֵחַ תּוֹכִיחַ אֶת־עֲמִיתֶךָ וְלֹא־תִשָּׂא עָלָיו חֵטְא
“Thou shalt not hate thy brother in thy heart: thou shalt certainly rebuke thy neighbour, and not suffer sin on his account.”
The Rambam’s words
Not to bear hatred in one's heart, as [Leviticus 19:17] states: "Do not hate your brother in your heart."
שלא לשנוא בלב, שנאמר "לֹא תִשְׂנָא אֶת אָחִיךָ בִּלְבָבֶךָ" (ויקרא יט, יז).
Why · Sefer HaChinuch #238
To not hate brothers
“The root of the commandment is well-known — as hatred of the heart causes great evils among people, being a constant ‘sword between a man and his brother’ and a man and his neighbor.”
Who & when
“And it is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Human Dispositions הלכות דעות