Musnad Ahmad 33:544

Aswad ibn Amir narrated to us, al-Hasan ibn Salih narrated to us, from Layth, from Abu al-Zubayr, from Jabir, who said: "The Messenger of Allah, may Allah bless him and grant him peace, would not sleep until he recited 'Alif Lam Mim, the revelation of the Prostration' (Surah as-Sajdah) and 'Blessed is He in whose hand is the dominion' (Surah al-Mulk)."