1 Samuel 24:3

Where was a cave This cave being near the highway, and in the most frequented place of the wilderness, namely, near the sheep-cotes, to which the shepherds and herdsmen resorted to feed and milk their flocks, it is likely David made choice of it as being a place most unlikely to be suspected. Or, perhaps, he was pressed so near by Saul that he had no other way of escaping. That his distress and danger were very great, may be gathered from the 57th and 142d Psalms, which, it is supposed, he composed in commemoration of his deliverance. Saul went in to cover his feet To take some rest in sleep. Being a military man, it is probable he used to sleep with his soldiers upon the ground. And it is not improbable that, being weary with his eager and almost incessant pursuit, first of David, then of the Philistines, and now of David again, he both needed and desired some sleep; God also disposing him thereto, that David might have this eminent occasion to demonstrate his integrity to Saul, and to all Israel. In the sides of the cave For that there were vast caves in those parts is affirmed, not only by Josephus, but also by heathen authors; Strabo writes of one which could receive four thousand men.