Deuteronomy 23:9-14

9When thou goest forth in camp against thine enemies, then thou shalt keep thee from every evil thing.

10If 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:

11but it shall be, when evening cometh on, he shall bathe himself in water: and when the sun is down, he shall come within the camp.

12Thou shalt have a place also without the camp, whither thou shalt go forth abroad:

13and thou shalt have a paddle among thy weapons; and it shall be, when thou sittest down abroad, thou shalt dig therewith, and shalt turn back and cover that which cometh from thee:

14for the LORD thy God walketh in the midst of thy camp, to deliver thee, and to give up thine enemies before thee; therefore shall thy camp be holy: that he see no unclean thing in thee, and turn away from thee.