Rashi on Deuteronomy 23:11/רש"י על דברים כ״ג:י״א

1מקרה לילה [IF THERE BE AMONG YOU ANY MAN THAT IS NOT CLEAN BY REASON OF] UNCLEANNESS THAT CHANCETH HIM BY NIGHT — By night: Scripture speaks of what usually occurs (but the law applies also if the uncleanness happens at day time) (Sifrei Devarim 255:3).

2ויצא אל מחוץ למחנה THEN HE SHALL GO ABROAD OUT OF THE CAMP — This is a command,

3לא יבא אל תוך המחנה HE SHALL NOT COME WITHIN THE CAMP — This is a prohibition (Sifrei Devarim 255:4). He is forbidden to enter the “camp of the Levites”, and all the more so, the "camp of the Shechinah". (cf. Sifrei Devarim 255:5; Pesachim 68a and Rashi on Numbers 5:2).