Negative commandment · Lo Ta’aseh #17 of 613
Not to show affection for a mesit
שלא לאהוב המסית
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 show affection for a mesit, as [Deuteronomy 13:9] states: "Do not show appreciation for him."
שלא לאהוב המסית, שנאמר "לא תאבה לו" (דברים יג,ט).
Why · Sefer HaChinuch #457
To not love the seducer
“From the roots of the commandment is like the matter that is written in the commandment that precedes it. And its colleague shall speak about all of its laws and practice.”
Where in the Mishneh Torah
Hilchot Foreign Worship and Customs of the Nations הלכות עבודה זרה וחוקות הגויים