Rashi on Numbers 19:7/רש"י על במדבר י״ט:ז׳

1אל המחנה [AND AFTERWARDS HE MAY COME] INTO THE CAMP — into the camp of the Shechina (in the case of the Temple at Jerusalem, into the forecourt, the עזרה, immediately in front of the Temple), from which alone he had been barred, for no unclean person was expelled from two camps (i.e. from more than one, viz., the מחנה שכינה) except a person with a running issue and a man who had experienced a seminal emission (who were expelled from the מחנה שכינה and מחנה לויה), and a leper (who had to remain outside all three) (cf. Pesachim 67a).

2וטמא הכהן עד הערב [AND AFTERWARDS HE SHALL COME INTO THE CAMP] AND THE PRIEST SHALL BE UNCLEAN UNTO THE EVENING — Invert its order (that of the phrases forming this half of the verse), and then explain it: He shall be unclean until the evening and afterwards he shall come into the camp (cf Rashi Leviticus 11:32 and Note thereon).