Musnad Ahmad 27:1015

Yazid ibn Harun narrated to us, Muhammad ibn Ishaq narrated to us, from Nafi’, who said: I heard a man from the Ansar, from the tribe of Banu Salama, narrating to Abdullah ibn Umar in the mosque, that a slave girl of Ka’b ibn Malik was grazing some sheep of his at Sal’. A sheep among them was struck by a mishap, and she feared for it, so she took a sharp stone and slaughtered it with it. They asked the Prophet, peace and blessings of Allah be upon him, about that, and he commanded them to eat it.