Jamieson, Fausset and Brown on Deuteronomy 21:22-23

22-23. if a man have committed a sin ... and thou hang him on a tree--Hanging was not a Hebrew form of execution (gibbeting is meant), but the body was not to be left to rot or be a prey to ravenous birds; it was to be buried "that day," either because the stench in a hot climate would corrupt the air, or the spectacle of an exposed corpse bring ceremonial defilement on the land.