Deuteronomy 23:14

Because the Lord thy God walketh about in thy camp, to save thee, and subdue thine enemy before thee, therefore thy camp must be holy. There must be nothing unseemly seen with thee, that He may not turn away from thee.

and thou shalt have a trowel on thy girdle; and it shall come to pass when thou wouldest relieve thyself abroad, that thou shalt dig with it, and shalt bring back the earth and cover thy nuisance.