John Gill Commentary 1 Samuel 3:9

"Therefore Eli said unto Samuel, Go, lie down: and it shall be, if he call thee, that thou shalt say, Speak, Jehovah; for thy servant heareth. So Samuel went and lay down in his place." — 1 Samuel 3:9 (ASV)

Therefore Eli said to Samuel, go, lie down
Once more;

and it shall be, if he call you ;
the voice, or the Lord by it:

that you shall say, speak, Lord, for your servant hears ;
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 to speak to him what he had to say, to which he was ready to attend:

so Samuel went and lay down in his place ;
which, as commonly understood, was in the court of the Levites, (See Gill on 1 Samuel 3:3).