Question: All agree that an item that was exchanged with an idol is prohibited. What is the status of an item that was exchanged with that item?

Answer (R. Chaninah): R. Yishmael bei R. Yosi prohibits it and Rabbanan permit it.

(R. Elazar bar Hoshiyah): The Rabbanan's source is the pasuk (Devarim 7:26), "(And you should not bring an abomination into your house) and become banned like it" - anything that comes from it is prohibited like it.

Question: How do we know that this includes even exchanges of exchanged items?

Answer (R. Yosi bei R. Bun): The Torah refers twice to banned items - once here and once in the pasuk (Devarim 13:18), "and nothing that is banned may cling to your hand" - these two are to teach that even exchanges of exchanged items are prohibited.