Ishmael's reason for dumping the bodies into a cistern was to cover up the earlier murder of Gedaliah. The cistern had been built by king Asa as a defense against Baasha king of Israel. This was the cistern that Ishmael son of Nethaniah filled with the slaughtered men.
Published by permission. Originally published by NavPress in English as THE MESSAGE: The Bible in Contemporary Language copyright 2002 by Eugene Peterson. All rights reserved. (The Message Bible Online)