I Samuel 3:9-11

Therefore Eli said to Samuel, “Go, lie down; and it shall be, if He calls you, that you must say, ‘Speak, LORD, for Your servant hears.’ ” So Samuel went and lay down in his place. Now the LORD came and stood and called as at other times, “Samuel! Samuel!” And Samuel answered, “Speak, for Your servant hears.” Then the LORD said to Samuel: “Behold, I will do something in Israel at which both ears of everyone who hears it will tingle.