1 Samuel 3:6-9

6And the Lord called yet again, “Samuel!” So Samuel got up and went to Eli and said, “Here I am, for you called me.” But he said, “I did not call, my son, go back and lie down.” 71Now Samuel did not yet know the Lord, nor had the word of the Lord yet been revealed to him. 8So the Lord called Samuel again for the third time. And he got up and went to Eli and said, “Here I am, for you called me.” Then Eli realized that the Lord was calling the boy. 9And Eli said to Samuel, “Go lie down, and it shall be if He calls you, that you shall say, ‘Speak, Lord, for Your servant is listening.’” So Samuel went and lay down in his place.