Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 13
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 13, with English translation by Maimonides (Rambam).
שלא ליטע אילן במקדש, שנאמר "לא תיטע לך אשרה, כל עץ" (דברים טז,כא).
Not to plant a tree on the Temple [premises], as [Deuteronomy 16:21] states: "Do not plant an asherah or any other tree...."