Musnad Abu Ya'la al-Mawsili 107:3

Abu Khaythama narrated to us, al-Walid ibn Muslim narrated to us, Abd al-Rahman ibn Yazid ibn Jabir narrated to us, from al-Qasim ibn Abd al-Rahman, from Uqbah ibn Amir, who said: While I was leading the Messenger of Allah (may Allah bless him and grant him peace) by the reins in one of those mountain passes, he said, "O Uqbah, will you not ride?" I felt it was too great a matter to ride the mount of the Messenger of Allah (may Allah bless him and grant him peace). Then he said, "O Uqbah, will you not ride?" I feared that it might be an act of disobedience, so the Messenger of Allah (may Allah bless him and grant him peace) dismounted, and I rode for a short while. Then he mounted. Then he said, "O Uqbah, shall I not teach you two surahs that are among the best two surahs that people recite?" I said, "Yes, O Messenger of Allah." He said, so he recited to me: "Say, I seek refuge in the Lord of the daybreak" (Qul a'udhu bi-rabbi al-falaq) and "Say, I seek refuge in the Lord of mankind" (Qul a'udhu bi-rabbi al-nas). Then the prayer was called, and the Messenger of Allah went forward and recited them. Then he passed by me and said, "How did you see them, O Uqbah? Recite them whenever you go to sleep and whenever you wake up."