Charles Ellicott Commentary 1 Samuel 22:1

"David therefore departed thence, and escaped to the cave of Adullam: and when his brethren and all his father`s house heard it, they went down thither to him." — 1 Samuel 22:1 (ASV)

The cave Adullam. —The great valley of Elah forms the highway from Philistia to Hebron. Especially in one of the tributary valleys or ravines of the Elah valley, there are many natural caves—some of great extent, roomy, and dry—which are still used by the shepherds as dwelling-places and as refuges for their flocks and herds. David chose one of these natural strongholds as the temporary home for himself and his followers. The traveller sees that there was ample room for the 400 refugees who gathered under David’s skilled leadership. Stanley even speaks of this Adullam Cavern as “a subterranean palace, with vast columnar halls and arched chambers.”

The name Adullam was probably given to the largest of these great caverns from its proximity to the old royal Canaanite city of Adullam (Joshua 15:35), the ruins of which, on a rounded hill to the south of the cave, are still visible.

His brothers and all his father’s house. —They, of course, soon felt the weight of Saul’s anger against the prominent hero of their race, and dreading the fate that often overwhelms whole families for the faults of one of their more distinguished members, fled from their homes, and joined David and his armed force of outlaws.