Negative commandment · Lo Ta’aseh #165 of 613
For a priest not to leave the Temple courtyard in the midst of service
שלא ייצא כוהן מן העזרה בשעת עבודה
The verse · Vayikra 10:7
וּמִפֶּתַח אֹהֶל מוֹעֵד לֹא תֵצְאוּ פֶּן־תָּמֻתוּ כִּי־שֶׁמֶן מִשְׁחַת ה׳ עֲלֵיכֶם וַיַּעֲשׂוּ כִּדְבַר מֹשֶׁה
“And you shall not go out from the door of the Tent of Meeting lest you die: for the anointing oil of the Lord is upon you. And they did according to the word of Moshe.”
The Rambam’s words
For a priest not to leave the Temple courtyard in the midst of service, as [implied by Leviticus 10:7]: "Do not depart from before the entrance to the Tent of Testimony."
שלא ייצא כוהן מן העזרה בשעת עבודה, שנאמר "ומפתח אוהל מועד לא תצאו" (ויקרא י,ז).
Who & when
“And [it] is practiced at the time of the [Temple] by the males of the priesthood.”
Where in the Mishneh Torah
Hilchot Admission into the Sanctuary הלכות ביאת מקדש