Musnad Ahmad 834:18

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Ubayd Allah ibn Talhah ibn Ubayd Allah ibn Kurayz al-Khuza'i narrated to me, from al-Hasan ibn Abi al-Hasan al-Basri, from 'Abd Allah ibn Mughaffal al-Muzani, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Do not pray in the resting places of camels, for they were created from the jinn. Do you not see their eyes and their state when they are startled? And pray in the enclosures of sheep, for they are closer to mercy."