"While I was leading the Messenger of Allah rode. Then he said: 'Shall I not teach you two of the best Surahs that the people recite?' And he taught me: 'Say: I seek refuge with (Allah) the Lord of the daybreak,' and 'Say: I seek refuge with (Allah) the Lord of mankind." Then the Iqamah was said and he went forward and recited them. Then he passed by me and said: 'What do you think, O 'Uqbah bin 'Amir? Recite them every time you go to sleep and get up.'"
Sunan an-Nasa'i Book 50, Hadith 10