Musnad Ahmad 482:75

Abu Sa'id narrated to us, Ibn Lahi'ah narrated to us, Mushrih narrated to us, he said: I heard 'Uqbah ibn 'Amir saying: The Messenger of Allah, peace and blessings of Allah be upon him, said to me: "Recite 'Say, I seek refuge in the Lord of the daybreak' (Al-Falaq) and 'Say, I seek refuge in the Lord of mankind' (An-Nas), for you will not recite anything like them."