Musnad Ahmad 907:157

'Abd al-Rahman ibn Mahdi narrated to us, Shu'bah narrated to us, from Simak, from Jabir ibn Samurah, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to recite in the Dhuhr prayer [the Surah] 'By the night when it covers' (Al-Layl). And in the 'Asr prayer, he would recite something similar to that. And in the morning [Fajr] prayer, he would recite something longer than that."