1 Samuel 3:8-9

8A third time the LORD called, “Samuel!” And Samuel got up and went to Eli and said, “Here I am; you called me.” Then Eli realized that the LORD was calling the boy.

9So 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.