9 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.

Matthew Henry's Commentary on Jeremiah 41:9

Commentary on Jeremiah 41:1-10

(Read Jeremiah 41:1-10)

Those who hate the worshippers of God, often put on the appearance of piety, that they may the easier hurt them. As death often meets men where they least expect it, we should continually search whether we are in such a state and frame of mind, as we would wish to be found in when called to appear before our Judge. Sometimes the ransom of a man's life is his riches. But those who think to bribe death, saying, Slay us not, for we have treasures in the field, will find themselves wretchedly deceived. This melancholy history warns us, never to be secure in this world. We never can be sure of peace on this side heaven.