Deuteronomy 23:9-11

New International Version - UK

Uncleanness in the camp

⁹ When you set up camp against your enemies, keep away from everything impure. ¹⁰ If one of your men is unclean because of a nocturnal emission, he is to go outside the camp and stay there. ¹¹ But as evening approaches he is to wash himself, and at sunset he may return to the camp.