Musannaf Ibn Abi Shayba 16:669

Abu Bakr narrated to us, he said: Abu Dawud al-Tayalisi narrated to us, from Imran al-Qattan, from Hammad, from Ibrahim, regarding feathers, heels (offspring), wool, and bones of a dead animal (as expiation for Zihar). He said: If it is washed, then that is its purification.