Deuteronomy 21:23
you must not leave the body on the tree overnight, but you must be sure to bury him that day, because anyone who is hung on a tree is under God’s curse. You must not defile the land that the LORD your God is giving you as an inheritance.
What it says
His body must be buried that day and not left overnight, because the one hung on a tree is under God's curse, and the land must not be defiled.
What it is doing
It gives the required burial and explains why prompt removal matters.
In context
22If a man has committed a sin worthy of death, and he is executed, and you hang his body on a tree, 23you must not leave the body on the tree overnight, but you must be sure to bury him that day, because anyone who is hung on a tree is under God’s curse. You must not defile the land that the LORD your God is giving you as an inheritance.