Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 230
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 230, with English translation by Maimonides (Rambam).
לתלות מי שנתחייב תלייה, שנאמר: "ותלית אותו, על עץ" (דברים כא,כב).
To hang [the corpses] of those liable for hanging, as [Deuteronomy 21:22] states: "And you shall hang them on a gallows."