Amr bin 'Asim al-Kalabi عمرو بن عاصم الكلابي · The Book on Sacrifices

"The Messenger of Allah (ﷺ) prohibited that an animal with a A'dab (stump) horn or ear should be slaughtered as a sacrifice." Qatadah (one of the narrators) said: "So I mentioned this to Sa'eed bin Al-Musayyab and he said: 'The A'dab is that which equals or more than that.'"