Musannaf Ibn Abi Shayba 3:1520

Ubayd Allah narrated to us, he said: Isra'il informed us, from Ash'ath ibn Abi al-Sha'tha', from Ja'far ibn Abi Thawr, from Jabir ibn Samurah, he said: The Messenger of Allah (may Allah bless him and grant him peace) commanded us to pray in the resting places of sheep, and not to pray in the resting places of camels.