Deuteronomy 23:9-11

Amplified Bible

⁹ “When you go out as an army [to fight] against your enemies, you shall keep yourselves from every evil [thing].

¹⁰ “If there is any man among you who is [ceremonially] unclean because of nocturnal emission, then he must go outside the camp; he shall not come back to the camp. ¹¹ But when evening comes, he shall bathe in water, and at sundown he may return to the camp.