Albert Barnes Commentary 1 Samuel 24:3

"And he came to the sheepcotes by the way, where was a cave; and Saul went in to cover his feet. Now David and his men were abiding in the innermost parts of the cave." — 1 Samuel 24:3 (ASV)

Remained in the sides - Rather, “were in the sides of the cave, dwelling or abiding there.” Some of these caverns are very deep and spacious. Anyone near the mouth of the cave would be visible, but those in the recesses would be completely in the dark and invisible, especially if the incident occurred at night. Psalms 67:1–7, according to its title, was composed on this occasion.