Musnad Ahmad 27:1063

Yahya ibn Sa'id al-Umawi narrated to us, from Yahya—meaning Ibn Sa'id—who said: Nafi' informed me that Ibn 'Umar informed them that a slave girl was herding sheep for the family of Ka'b ibn Malik al-Ansari. She feared that one of the sheep was going to die, so she took a stone and slaughtered it with it. This was mentioned to the Prophet, peace and blessings of Allah be upon him, and he commanded them to eat it.