the reward of listening

The boy Samuel ministered before the Lord under Eli. In those days the word of the Lord was rare; there were not many visions.  One night Eli, whose eyes were becoming so weak that he could barely see, was lying down in his usual place.

The lamp of God had not yet gone out, and Samuel was lying down in the temple of the Lord, where the ark of God was.

Then the Lord called Samuel. Samuel answered, "Here I am."

And he ran to Eli and said, "Here I am; you called me." But Eli said, "I did not call; go back and lie down." So he went and lay down. Again the Lord called, "Samuel!" And Samuel got up and went to Eli and said, "Here I am;  you called me." "My son," Eli said, "I did not call; go back and lie down."

Now Samuel did not yet know the Lord: The word of the Lord had not yet been revealed to him.

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

The Lord came and stood there, calling as at the other times, "Samuel! Samuel!"  Then Samuel said, "Speak, for your servant is listening." 
1 Samuel 3:1-10 (NIV)