Musnad Ahmad 538:6

Ali ibn Bahr narrated to us, he said: Al-Walid ibn Muslim narrated to us, Abdullah—meaning Ibn Zabr—narrated to us, that he heard Muslim ibn Mishkam saying: Abu Thalaba al-Khushani narrated to us, he said: When the Messenger of Allah (peace and blessings of Allah be upon him) would descend at a place and set up camp, the people would disperse from him into the mountain passes and the valleys. So he stood among them and said: "Verily, your dispersing in the mountain passes and the valleys is only from Satan." He said: So after that, when they would descend, they would gather close to one another, until you would say: "If a garment were spread over them, it would cover them all," or something similar to that.