Musnad Ahmad 32:1351

'Abd al-Wahhab narrated to us, he said: Hisham informed us, from Qatadah, from Anas ibn Malik, that the Prophet of Allah, may Allah bless him and grant him peace, said: "The distance between the two sides of my Hawd (Cistern) is like the distance between San'a and al-Madinah," or "like the distance between al-Madinah and 'Amman" — Hisham was in doubt.