1 Samuel 3:9-10 ESV
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.
And the LORD came and stood, calling as at other times, “Samuel! Samuel!” And Samuel said, “Speak, for your servant hears.”
ESV: English Standard Version 2016