Musnad Abu Ya'la al-Mawsili 154:54

Zuhayr narrated to us, Waki' narrated to us, from Hisham, from his father, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not intend your prayer at the rising of the sun, for it rises between the two horns of Satan."