It is narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Shall I not tell you of the best thing with which those who seek refuge seek refuge: Surah al-Falaq and Surah al-Nas."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15014