Positive commandment · Mitzvat Aseh #31 of 613
Send the impure out of the camp of the Divine Presence
לשלח טמאים ממחנה שכינה שהוא המקדש
The verse · Bamidbar 5:2
צַו אֶת־בְּנֵי יִשְׂרָאֵל וִישַׁלְּחוּ מִן־הַמַּחֲנֶה כׇּל־צָרוּעַ וְכׇל־זָב וְכֹל טָמֵא לָנָפֶשׁ
“Command the children of Yisra᾽el, that they put out of the camp everyone with żara῾at, and everyone that has an issue, and whoever is defiled by the dead:”
The Rambam’s words
To send impure people out from the camp of the Divine Presence - i.e., the sanctuary - as [Numbers 5:2] states: "And you shall send from the camp all the leprous, any zav, and anyone who has contracted impurity because of a corpse."
לשלח טמאים ממחנה שכינה שהוא המקדש, שנאמר: "וִישַׁלְּחוּ מִן הַמַּחֲנֶה כָּל צָרוּעַ וְכָל זָב וְכֹל טָמֵא לָנֶפֶשׁ" (במדבר ה, ב).
Why · Sefer HaChinuch #362
Send the impure out of the camp of the Divine Presence
“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 at all times.”
Where in the Mishneh Torah
Hilchot Admission into the Sanctuary הלכות ביאת מקדש