Musnad Ahmad 32:730

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Qatadah, from Anas ibn Malik, that the Prophet, peace and blessings of Allah be upon him, said: "The Lote Tree of the Utermost Boundary (Sidrat al-Muntaha) was raised up for me in the seventh heaven. Its fruits were like the jars of Hajar, and its leaves were like the ears of elephants. From its trunk emerge two manifest rivers and two hidden rivers. I said: 'O Gabriel, what are these?' He said: 'As for the hidden ones, they are in Paradise, and as for the manifest ones, they are the Nile and the Euphrates.'"