Musnad Ahmad 961:120

'Abd al-Samad ibn 'Abd al-Warith narrated to us, 'Umar ibn Ibrahim narrated to us, Qatadah narrated to us, from al-'Ala' ibn Ziyad, from a man who narrated to him whom he trusted, from Mu'adh ibn Jabal, from the Messenger of Allah (peace and blessings of Allah be upon him): "Indeed, the devil is the wolf of man, like the wolf of sheep; he takes the stray sheep and the one that wanders off. So beware of the mountain paths, and adhere to the group and the general public."