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.
To make way for the account of God's revealing himself first to Samuel, we are here told, 1. How industrious Samuel was in serving God, according as his place and capacity were (Sa1 3:1): The child Samuel, though but a child, ministered unto the Lord before Eli. It was an aggravation of the wickedness of Eli's sons that the child Samuel shamed them.
Commenting on 1 Samuel 3:1-10
Therefore Eli said unto Samuel, go, lie down,.... Once more: and it shall be, if he call thee; the voice, or the Lord by it: that thou shalt say, speak, Lord, for thy servant heareth; his meaning is, that he should not rise and come to him, as he had done, but continue on his bed, on hearing the voice again, but desire the Lord...
Speak, Lord; for thy servant heareth - This was the usual way in which the prophets spoke, when they had intimations that the Lord was about to make some especial revelation.