The Messenger of Allah ﷺ forbade sacrificing an animal with a broken horn or a defective ear.Qatada said, "I mentioned this to Saeed bin Musayab, and he said, 'Adab refers to a defect that affects half of the horn or ear, or more than that.'"
حدثنا هناد حدثنا عبدة عن سعيد عن قتادة عن جري بن كليب النهدي
نهى رسول الله ﷺ أن يضحى بأعضب القرن والأذن قال قتادة فذكرت ذلك لسعيد بن المسيب فقال العضب ما بلغ النصف فما فوق ذلك
Sourcing, hasan. Ibn Majah also narrated it, no. 3145, from the hadith of Saeed bin Abu Aruba with the same wording. Shubah narrated it from Qatada with the same wording, as found in Nasai, no. 4382, and in Bazzar's Al-Bahr Al-Zakhkhar, 3/96, no. 876. The hadith of Ibn Kulayb is hasan, according to the preferred view.