Musnad Ahmad 32:1921

'Affan narrated to us, Hammad ibn Zayd narrated to us, he said: I heard Thabit narrating from Anas ibn Malik, he said: "The Messenger of Allah (peace and blessings of Allah be upon him) was the bravest of people, the best of people, and the most generous of people." He said: The people of Medina were alarmed one night. He said: The people set out toward the sound, but the Messenger of Allah (peace and blessings of Allah be upon him) met them, having already preceded them, and he was saying: "Do not be alarmed." He said: And he was upon a horse belonging to Abu Talha, unsaddled, with a sword around his neck. He began saying to the people: "Do not be alarmed." He said: And he said: "We found it to be a sea," or "It is indeed a sea," meaning the horse.