Jeremiah 31:40 - Ellicott's Commentary On The Whole Bible

The whole valley of the dead bodies... — We have to think of this city as Jeremiah saw it during the horrors of the siege — the lower part, the “plain” or “valley” of the city, the valley of Hinnom (comp. Jeremiah 19:11), filled with corpses lying unburied in the streets (Lamentations 2:21; Lamentations 4:9), the “ashes” of burnt and shattered houses encumbering the streets with their débris, the fields or open spaces that stretched to the Kidron valley, and the “horse-gate” by the king’s palace (2 Kings 11:16; 2 Chronicles 23:15; Nehemiah 3:28) — all this now lay before him as a scene of unspeakable desolation; but in his vision of the restored city he sees it all cleansed from whatever was defiling, consecrated to Jehovah, and holy as the precincts of the Temple. It is, perhaps, not without significance in connection with this passage, that when the city was restored, the region above the “horse-gate” was repaired by the priests, who seem to have had their houses in that quarter (Nehemiah 3:28-29). They appear to have been anxious to restore the sanctity of that over which Jeremiah had lamented as desecrated and defiled. The word for “ashes” was a technical one (Leviticus 6:10-11) for the refuse which remained on the altar after a burnt-offering, and which was to be carried without the camp (Leviticus 4:12; Leviticus 6:11). Probably this and the sweepings of the Temple were thrown into the valley of Hinnom.