Negative commandment · Lo Ta’aseh #18 of 613
Not to reduce one's hatred for a mesit
שלא לעזוב השנאה למסית
The verse · Devarim 13:9
לֹא־תֹאבֶה לוֹ וְלֹא תִשְׁמַע אֵלָיו וְלֹא־תָחוֹס עֵינְךָ עָלָיו וְלֹא־תַחְמֹל וְלֹא־תְכַסֶּה עָלָיו
“thou shalt not consent to him, nor hearken to him; nor shall thy eye pity him, nor shalt thou spare, nor shalt thou conceal him:”
The Rambam’s words
Not to reduce one's hatred for a mesit, as [Deuteronomy 13:9] states: "Do not listen to him."
שלא לעזוב השנאה למסית, שנאמר "ולא תשמע אליו" (דברים יג,ט).
Why · Sefer HaChinuch #458
To not leave the hatred towards the seducer
“It is from the roots of the commandment like the matter of the two previous commandments — as it is all to distance every matter of idolatry, that we not stumble in it in any way.”
Where in the Mishneh Torah
Hilchot Foreign Worship and Customs of the Nations הלכות עבודה זרה וחוקות הגויים