I Samuel 3:9

9 So Eli told Samuel, "Go and lie down, and if he calls you, say, 'Speak, Lord, for your servant is listening.'" So Samuel went and lay down in his place.

9 So Eli said to Samuel, Go back: and if the voice comes again, let your answer be, Say on, Lord; for the ears of your servant are open. So Samuel went back to his bed.