Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 164
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 164, with English translation by Maimonides (Rambam).
שלא ייכנס כוהן למקדש קרוע בגדים, שנאמר "ובגדיכם לא תפרומו" (ויקרא י,ו).
For a priest not to enter the Temple with torn garments, as [implied by Leviticus, ibid.]: "Do not rend your garments."