Musnad Ahmad 907:107

Abdullah narrated to us, Khalaf ibn Hisham al-Bazzar al-Muqri narrated to me, Abu al-Ahwas narrated to us, from Simak, from Jabir ibn Samurah, who said: "When the Messenger of Allah (peace and blessings of Allah be upon him) prayed the dawn prayer, he would sit in his place of prayer until the sun rose."