Musnad Ahmad 30:2820

'Abd al-Rahman narrated to us, he said: Shu'bah narrated to us, from Abu al-Dahhak, he said: I heard Abu Hurayrah saying: The Messenger of Allah, may Allah bless him and grant him peace, said: "Indeed, in Paradise there is a tree; the rider travels in its shade for one hundred years without crossing it; the tree of eternity."