Musnad Abu Ya'la al-Mawsili 65:8

Muhammad ibn al-Muthanna narrated to us, al-Ansari narrated to us, al-Ash'ath narrated to us, from al-Hasan, from Jundub ibn Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever performs the morning prayer is under the protection of Allah. So beware, lest Allah should seek you for anything regarding His protection."