The Valley of Hinnom had a history: child-sacrifice, Josiah’s defilement, Jeremiah’s “valley of slaughter.” Jesus picks up a loaded place-name.
Jeremiah said the valley would be called the Valley of Slaughter when Jerusalem fell. Bodies, fire, worms — that is siege-and-aftermath language the first hearers already knew.
Matthew 5, 10, and 18 use Gehenna in discipleship warnings aimed at a people heading toward that city’s end. Reading every Gehenna text as a cosmology of souls skips the lawsuit Jesus is filing against that generation.
When Jerusalem burned, the idiom became visible. That does not empty moral seriousness. It locates the warning where Jesus located it.
The New Creation is not lived under a valley-threat from a city that already fell. Holiness now is life in the unshakable kingdom.