Jeremiah 31:40
And the whole valley of the dead bodies, and of the ashes, and all the fields unto the brook of Kidron, unto the corner of the horse gate toward the east, shall be holy unto the LORD; it shall not be plucked up, nor thrown down any more for ever.
Jeremiah was directed to commit his message to writing immediately following the exchange of letters between himself and the elders held in Babylonian captivity. That written record, comprising Jeremiah 30 and Jeremiah 31, set forth all that had been revealed concerning the restoration of Israel. Within it the promise of the return stands sure, and the testimony concerning seventy years to be accomplished in the desolations of Jerusalem is stated very plainly.
Together with Jeremiah 25 and Jeremiah 27-29, this writing was studied by Daniel in the first year of Darius the Mede, more than sixty years after it had been written. As he studied, Daniel was perplexed over the relation of the seventy years of captivity to the twenty-three hundred years that were to elapse before the cleansing of the sanctuary.