1 Samuel 24:3, 8

He came to the sheepfolds on the way, where there was a cave; and Saul went in to relieve himself. Now David and his men were sitting in the inner recesses of the cave.

Now afterward David arose and went out of the cave and called after Saul, saying, “My lord the king!” And when Saul looked behind him, David bowed with his face to the ground and prostrated himself.