Musnad Abu Ya'la al-Mawsili 111:45

Abdullah ibn Umar narrated to us, Muhammad ibn Fudayl narrated to us, from al-Walid ibn Jami’, from the one who narrated to him, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Close up your rows, for I see the devils passing between you as if they were the young of the *hadhaf* (a type of small black sheep)."