"who shall not be clean because of a nocturnal accident": This tells me only of a nocturnal accident (i.e., emission). Whence do I derive (the same for) a diurnal accident? From "who shall not be clean" — in any event. Why, then, is it written "a nocturnal accident"? Scripture speaks of the common instance.
"then he shall go outside the camp" — this is a positive commandment;
"he shall not come into the midst of the camp" — this is a negative commandment. R. Shimon Hatemani says: "then he shall go outside the camp" — this is the Levite camp; "he shall not come into the midst of the camp" — this is the camp of the Shechinah.