Musnad Ahmad 27:1014

Yazid ibn Harun narrated to us, Yahya—meaning Ibn Sa'id—informed us, from Nafi', that he informed him from Ibn 'Umar, that a woman was herding sheep for the family of Ka'b ibn Malik at Sal'. She feared that one of them would die, so she slaughtered it with a stone. That was mentioned to the Messenger of Allah, may Allah bless him and grant him peace, and he commanded them to eat it.