Parashas Eikev · Passuk 7:26
You must not bring an abhorrent thing into your house, or you will be proscribed like it; you must reject it as abominable and abhorrent, for it is proscribed.
Torah Temimah points to Temurah 30b.
TT lemma: והיית חרם כמהו (unit 5 of 7).
English: Rav Achadvoi bar Ami said in the name of Rav: One who betroths with the dung of calves of idolatry — she is not betrothed, as it is said, “you shall become banned like it”: whatever you generate from it is like it. Related derivation also appears from “nothing of the banned property shall cling to your hand” (Re’eh).
Custom (dung of idolatrous calves — kiddushin)
Even dung generated from idolatrous animals cannot effect betrothal; it is treated like the ban itself.