Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 193
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 193, with English translation by Maimonides (Rambam).
להתקין יתד, שנאמר: "ויתד תהיה לך, על אזנך" (דברים כג,יד).
To prepare a shovel [to cover one's excrement], as [Deuteronomy 23:14] states: "You shall have a shovel in addition to your weapons."