Negative commandment · Lo Ta’aseh #50 of 613
Not to show favor to the worshipers of false gods
שלא לחון על עובדי עבודה זרה
The verse · Devarim 7:2
וּנְתָנָם ה׳ אֱלֹהֶיךָ לְפָנֶיךָ וְהִכִּיתָם הַחֲרֵם תַּחֲרִים אֹתָם לֹא־תִכְרֹת לָהֶם בְּרִית וְלֹא תְחׇנֵּם
“and when the Lord thy God shall deliver them before thee, and thou shalt smite them, then thou shalt devote them to utter destruction; thou shalt make no covenant with them, nor show mercy to them:”
The Rambam’s words
Not to show favor to the worshipers of false gods, as [Deuteronomy 7:2] states: "Do not show them favor."
שלא לחון על עובדי עבודה זרה, שנאמר "ולא תחונם" (דברים ז,ב).
Why · Sefer HaChinuch #426
To not favor or have mercy on an idolater
“It is from the roots of the commandment [that it is] since the beginning of any action of people is the fixing of the thought about the actions and the bringing up of the words upon the language of the tongue [about them]; and [only] after the thought and the speech about them, will he do any action.”
Who & when
“And this commandment is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Foreign Worship and Customs of the Nations הלכות עבודה זרה וחוקות הגויים