Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[120] But for the king himself, he was not at all irritated against Jeremiah, such was his gentle and righteous disposition; yet, that he might not be engaged in a quarrel with those rulers at such a time, by opposing what they intended, he let them do with the prophet whatsoever they would; whereupon, when the king had granted them such a permission, they presently came into the prison, and took him, and let him down with a cord into a pit full of mire, that he might be suffocated, and die of himself. So he stood up to the neck in the mire which was all about him, and so continued; but there was one of the king's servants, who was in esteem with him, an Ethiopian by descent, who told the king what a state the prophet was in, and said that his friends and his rulers had done evil in putting the prophet into the mire, and by that means contriving against him that he should suffer a death more bitter than that by his bonds only. When the king heard this, he repented of his having delivered up the prophet to the rulers, and bid the Ethiopian take thirty men of the king's guards, and cords with them, and whatsoever else they understood to be necessary for the prophet's preservation, and to draw him up immediately. So the Ethiopian took the men he was ordered to take, and drew up the prophet out of the mire, and left him at liberty [in the prison].