Musnad Ahmad 37:5

Zayd ibn al-Hubab narrated to us, saying: Abd al-Malik ibn al-Rabi’ ibn Sabrah al-Juhani narrated to me, from his father, from his grandfather, who said: "The Messenger of Allah, may Allah bless him and grant him peace, forbade us from praying in the resting places of camels, and from praying in the enclosures of sheep."