Jeremiah 38:6-7

So they took Jeremiah and threw him into the cistern of Malchijah the king’s son, which was in the court of the guardhouse; and they let Jeremiah down [into the cistern] with ropes. Now there was no water in the cistern but only mud, and Jeremiah sank in the mud. Now Ebed-melech the Ethiopian (Cushite), one of the eunuchs who was in the king’s palace, heard that they had put Jeremiah in the cistern, and while the king was sitting in the Gate of Benjamin