Musnad Abu Ya'la al-Mawsili 111:1

Amr ibn Husayn narrated to us, Hafs ibn Ghiyath al-Nakha'i narrated to us, Ibn Jurayj narrated to me, from 'Ata', from Ibn 'Abbas, who said: A man said, "O Messenger of Allah, a camel (badana) has become obligatory upon me, but camels have become scarce, so what do you see?" He said, "Slaughter in its place seven sheep."