A glass of water

A small boy is sent to bed by his father. Five minutes later: "Da-ad... " "What? " "I'm thirsty. Can you bring me a glass of water? "No. You had your chance. Lights out." Five minutes later: "Da-aaaad... " "WHAT? " "I'm THIRSTY... Can I have a glass of water?? " "I told you NO! If you ask again I'll have to spank you!!" Five minutes later... "Daaaa-aaaad... " "WHAT??!! " "When you come in to spank me, can you bring me a glass of water? "