John Gill Commentary Deuteronomy 23:10

"If there be among you any man, that is not clean by reason of that which chanceth him by night, then shall he go abroad out of the camp, he shall not come within the camp:" — Deuteronomy 23:10 (ASV)

If there be among you any man that is not clean
Any unclean person in the army, that was even ceremonially unclean in any of the instances the law makes so, one of which put for the rest is mentioned:

by reason of uncleanness that chanceth him by night ;
through pollution by a nocturnal flux, as the Septuagint version, or a gonorrhoea, an involuntary one, occasioned by impure thoughts and imaginations in dreams; the same case as in (Leviticus 15:16)

then shall he go abroad out of the camp ;
out of the army, lest others should be defiled by such; they not having houses to retire to, and chambers to keep themselves in separate from others, as when at home:

he shall not come within the camp ;
that is, not till he has done what is prescribed him in the next verse. Jarchi says, he might not come into the camp of the Levites, and much less into the camp of God.