Musnad Ahmad 529:15

'Ali ibn Bahr narrated to us, he said: 'Isa ibn Yunus narrated to us, he said: Thawr ibn Yazid narrated to us, Abu Humayd al-Ru'ayni narrated to me, he said: Yazid Dhu Misr informed me, he said: I came to 'Utbah ibn 'Abd al-Sulami and said: "O Abu al-Walid, I went out seeking animals for sacrifice, but I did not find anything that pleased me except for a *tharma'* (an animal with broken front teeth). What do you say?" He said: "Why did you not bring it to me?" I said: "Subhan Allah! Is it permissible for you and not permissible for me?" He said: "Yes, for you are in doubt and I am not in doubt. The Messenger of Allah (peace and blessings of Allah be upon him) only forbade the *musaffarah*, the *musta'salah*, the *bakhqa'*, the *mushayya'ah*, and the *kasra'*." The *musaffarah* is the one whose ear is cut off until its ear canal appears. The *musta'salah* is the one whose horn is uprooted from its base. The *bakhqa'* is the one whose eye is blinded. The *mushayya'ah* is the one that does not follow the flock due to emaciation, weakness, and inability. The *kasra'* is the one that has no marrow.