Musnad Abu Ya'la al-Mawsili 115:150

Ahmad ibn al-Miqdam narrated to us, Mu'tamir narrated to us, he said: I heard my father narrating from Qatadah, from Anas, from the Prophet (peace and blessings of Allah be upon him), who said: "Indeed, there is a tree in Paradise; a rider travels in its shade for a thousand years without crossing it."