Deuteronomy 23:12

10If there is among you any man who is not clean by reason of that which happens to him by night, then shall he go outside of the camp. He shall not come within the camp;

11but it shall be, when evening comes, he shall bathe himself in water. When the sun is down, he shall come within the camp.

12You shall have a place also outside of the camp where you go relieve yourself.

13You shall have a trowel among your weapons. It shall be, when you relieve yourself, you shall dig with it, and shall turn back and cover your excrement;

14for the LORD your God walks in the middle of your camp, to deliver you, and to give up your enemies before you. Therefore your camp shall be holy, that he may not see an unclean thing in you, and turn away from you.