Jamieson, Fausset and Brown on 1 Samuel 30:16

16. they were spread abroad upon all the earth--Believing that David and all his men of war were far away, engaged with the Philistine expedition, they deemed themselves perfectly secure and abandoned themselves to all manner of barbaric revelry. The promise made in answer to the devout inquiries of David (1Sa 30:8) was fulfilled. The marauders were surprised and panic-stricken. A great slaughter ensued--the people as well as the booty taken from Ziklag was recovered, besides a great amount of spoil which they had collected in a wide, freebooting excursion.