8 And the Lord called Samuel again the third time. And he arose and went to Eli and said, "Here I am, for you called me." Then Eli perceived that the Lord was calling the young man. 9 Therefore Eli said to Samuel, "Go, lie down, and if he calls you, you shall say, 'Speak, Lord, for your servant hears.'" So Samuel went and lay down in his place.
Matthew Henry's Commentary on 1 Samuel 3:8-9
Commentary on 1 Samuel 3:1-10
(Read 1 Samuel 3:1-10)
The call which Divine grace designs shall be made effectual; will be repeated till it is so, till we come to the call. Eli, perceiving that it was the voice of God that Samuel heard, instructed him what to say. Though it was a disgrace to Eli, for God's call to be directed to Samuel, yet he told him how to meet it. Thus the elder should do their utmost to assist and improve the younger that are rising up. Let us never fail to teach those who are coming after us, even such as will soon be preferred before us, John 1:30. Good words should be put into children's mouths betimes, by which they may be prepared to learn Divine things, and be trained up to regard them.