Judges 20:38

And the children of Israel had a signal of battle with the liers in wait, that they should send up a signal of smoke from the city.

Now there was an appointed sign between the men of Israel and the liers in wait, that they should make a great flame with smoke rise up out of the city.

Now the appointed sign between the men of Israel and the ambushers was that they should make a great cloud of smoke rise up out of the city.