Musannaf Ibn Abi Shayba 3:5794

Abu al-Ahwas narrated to us, from Ibn Abi Ishaq, from Abu al-Safar, who said: I saw Abdullah ibn Mughaffal in al-Mada'in, and I said: "I am the imam of my people, and I intend to return to my family, so how many [rak'ahs] should I pray?" He said: "Four." Then I met him later in al-Rayy, and I said: "I intend to return to my family, so how many do you command me to pray?" He said: "Two."