Ben strikes again

Soooo today, when decided to talk back to me. I told him that if he did that again I'd wash his mouth out with soap. (not really planning on doing it, but hoping the threat would make a good impact)
Ben goes in the bathroom, I assume to wash his hands. He comes out and I see white stuff all around his mouth. "What's that Ben?"...He answers "Soap"
Oi!