Musnad Ahmad 947:6

Al-Walid ibn Muslim narrated to us, Al-Awza'i narrated to us, Hassan ibn 'Atiyyah narrated to us, from Abu Waqid al-Laythi: That they said, "O Messenger of Allah, we are in a land where we are afflicted by famine, so when is the dead animal (carrion) permissible for us?" He said, "If you do not have a morning meal, and you do not have an evening meal, and you do not have anything to cook (or gather), then it is yours to consume."