Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 35
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 35, with English translation by Maimonides (Rambam).
שלא לחבור חבר, שנאמר "וחובר, חבר" (דברים יח,יא).
Not to cast spells, as [Deuteronomy 18:11] states: "[There shall not be found among you...] one who casts spells."