Ezekiel 6:13
Then shall ye know that I am the LORD, when their slain men shall be among their idols round about their altars, upon every high hill, in all the tops of the mountains, and under every green tree, and under every thick oak, the place where they did offer sweet savour to all their idols.
The prophecy declares that God would break down the high places of Israel's idolatry, scattering the slain among their idols and round about their altars on every high hill, on the tops of the mountains, under every green tree and under every thick oak where sweet savour had been offered to idols, and that by this desolation the people would know that He is the LORD. The slain lying in the very places of false worship would be the sign of divine judgment executed against idolatrous shrines.
This word was fulfilled in the Roman overthrow of Judea, which pursued the nation from city to city until its last stand ended at Masada. There nine hundred and sixty lay slain together in the fortress set upon the high rock, a final heap of the dead upon the high place answering to the slain upon every high hill foretold. That end proved the anger of God for manifold sins, showing that He had condemned the Jewish nation to destruction and deserted them to their enemies.