Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 48
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 48, with English translation by Maimonides (Rambam).
שלא לכרות ברית לשבעה עממין, שנאמר "לא תכרות להם ברית" (דברים ז,ב).
Not to establish a covenant with the seven [Canaanite] nations, as [Deuteronomy 7:2] states: "Do not establish a covenant with them."