Musnad Ahmad 32:2156

Bahz narrated to us, Shu'bah narrated to us, Qatadah narrated to us, from Anas ibn Malik, who said: There was a state of alarm in Medina. The Prophet, peace and blessings of Allah be upon him, borrowed a horse belonging to Abu Talhah, which was called Mandub. He rode it, and then said: "We have not seen any alarm, and we have found it to be a sea."