John Gill Commentary 1 Samuel 24:8

"David also arose afterward, and went out of the cave, and cried after Saul, saying, My lord the king. And when Saul looked behind him, David bowed with his face to the earth, and did obeisance." — 1 Samuel 24:8 (ASV)

David also arose afterward after Saul was gone, and went out of the cave where he had been all the time that Saul had been in it. He cried after Saul with a loud voice, "My lord the king," by which titles Saul would know that he was called unto. And when Saul looked behind him to see who it was that called unto him, David stooped with his face to the earth, and bowed himself, giving reverence and honour to him as a king (See Gill on 1 Samuel 20:41).