Negative commandment · Lo Ta’aseh #77 of 613
For a priest who is ritually impure not to enter the Temple courtyard
שלא יכנס טמא לעזרה
The verse · Bamidbar 5:3
מִזָּכָר עַד־נְקֵבָה תְּשַׁלֵּחוּ אֶל־מִחוּץ לַמַּחֲנֶה תְּשַׁלְּחוּם וְלֹא יְטַמְּאוּ אֶת־מַחֲנֵיהֶם אֲשֶׁר אֲנִי שֹׁכֵן בְּתוֹכָם
“both male and female shall you put out, outside the camp shall you put them; that they defile not their camps, in the midst of which I dwell.”
The Rambam’s words
For a priest who is ritually impure not to enter the Temple courtyard, as [Numbers 5:3] states: "And they shall not make your camp impure." This refers to the camp of the Divine Presence.
שלא יכנס טמא לעזרה, שנאמר "וְלֹא יְטַמְּאוּ אֶת מַחֲנֵיהֶם" (במדבר ה, ג); זה מחנה שכינה.
Why · Sefer HaChinuch #363
That an impure person not enter the entire Temple
“It is from the roots of the commandment [that it is] because it is known to the Sages that the matter of impurity weakens the power of the intellect and mixes it up and separates between it and the pure and perfect Elevated Understanding.”
Who & when
“And this commandment is practiced by males and females.”
Where in the Mishneh Torah
Hilchot Admission into the Sanctuary הלכות ביאת מקדש