John Gill Commentary Judges 20:47

"But six hundred men turned and fled toward the wilderness unto the rock of Rimmon, and abode in the rock of Rimmon four months." — Judges 20:47 (ASV)

But six hundred men
Who were all that were left of 26,700

turned and fled to the wilderness ;
turned out of the highway or common road, and being swift of foot, got to a wilderness; what wilderness is not certain:

unto the rock Rimmon, and abode in the rock Rimmon four months ;
very probably in a cave of that rock, which might be large enough to hold such a number; Saul is said to have just the same number under it, and David had also a like number in a cave at Engedi, (1 Samuel 14:2) (23:13) (24:3) , and from hence these men might send out of their number to fetch in provision for them from parts adjacent, after the heat of the action was over, and the rage and fury of the Israelites subsided.