Deuteronomy 23:13-14

13and you shall have a spade among your tools, and when you [prepare to] sit down outside [to relieve yourself], you shall dig a hole with it and shall turn and cover up your waste.

14Since the Lord your God walks in the midst of your camp to rescue you and to defeat your enemies before you, therefore your camp must be holy (undefiled); and He must not see anything indecent among you or He will turn away from you.