Hadith 891:2
Isma'il narrated to us, al-Jariri informed us, from Abu al-'Ala', who said: A man said: We were with the Messenger of Allah, peace and blessings of Allah be upon him, on a journey, and the people were taking turns [riding], and there was a scarcity of mounts. The turn of the Messenger of Allah, peace and blessings of Allah be upon him, came, and my turn came. He caught up with me from behind and struck my shoulder, then said: "Say: I seek refuge in the Lord of the daybreak." So I said: "I seek refuge in the Lord of the daybreak," and the Messenger of Allah, peace and blessings of Allah be upon him, recited it, and I recited it with him. Then he said: "Say: I seek refuge in the Lord of mankind." So the Messenger of Allah, peace and blessings of Allah be upon him, recited it, and I recited it with him. Then he said: "When you pray, recite them both."
حدثنا إسماعيل، أخبرنا الجريري، عن أبي العلاء، قال: قال رجل: كنا مع رسول الله صلى الله عليه وسلم في السفر، والناس يعتقبون، وفي الظهر قلة، فحانت نزلة رسول الله صلى الله عليه وسلم، ونزلتي، فلحقني من بعدي فضرب منكبي، فقال: " قل: أعوذ برب الفلق "، فقلت: أعوذ برب الفلق، فقرأها رسول الله صلى الله عليه وسلم، وقرأتها معه، ثم قال: " قل: أعوذ برب الناس "، فقرأها رسول الله صلى الله عليه وسلم، وقرأتها معه، فقال: " إذا صليت فاقرأ بهما "