Maliks Muwatta Book 24, Hadith Number 4.
Section : Methods of Slaughter Permitted in Necessity.
Yahya related to me from Malik from Nafi from a man of the Ansar from Muadh ibn Sad or Sad ibn Muadh that a slave-girl of Kab ibn Malik was herding some sheep at Sal (a mountain near Madina). One of the sheep was about to die, so she went over to it and slaughtered it with a stone. The Messenger of Allah, may Allah bless him and grant him peace, was asked about that, and he said, “There is no harm in it, so eat it.”