You must have a place outside the camp to go and relieve yourself.
Israel was now encamped, and this vast army was just entering upon action, which was likely to keep them together for a long time, and therefore it was fit to give them particular directions for the good ordering of their camp. And the charge is in one word to be clean. They must take care to keep their camp pure from moral, ceremonial, and natural pollution. I.
Commenting on Deuteronomy 23:9-14
Thou shalt have also a place without the camp,.... A place prepared, as the Targums of Onkelos and Jonathan, provided on purpose for the use hereafter suggested; so Ben Melech: whither thou shalt go forth abroad; to do the necessities of nature, which they were to do without the camp, not in any place they thought fit and most convenient, but what was appointed for that purpose.
Thou shalt have a place also without the camp, whither thou shalt (f) go forth abroad: (f) For the necessities of nature.