Eli understands

8And Yahweh called Samuel again a third time. So he got up and went to Eli and said, “Here I am, for you called me.” Then Eli understood that Yahweh was calling the boy.

9Then Eli said to Samuel, “Go, lie down, and if he calls to you, you shall say, ‘Speak, Yahweh, for your servant is listening.’” So Samuel went and lay down in his place.