When does Jace say that about the rubber duckie and the electric eel?

"Just because Ты call an eletric угорь a rubber duck, doesn't make it a rubber duck, does it? And God help the poor bastard who decides they want to take a bath with the duckie"

It's in the Forsaken chapter of 'City of Bones'. They're in the weapons room and they're talking about the seraph blades and how Clary thought they were made from magic, which lead Jace to say the quote above. Hope that helped.