Musnad Ahmad 482:32

Yahya ibn Ishaq narrated to us, he said: Ibn Lahi'ah narrated to us, from Musharrah ibn Ha'an, from Uqbah ibn Amir, he said: The Messenger of Allah, may Allah bless him and grant him peace, said to me: "Recite the two refuge-seeking surahs (Al-Mu'awwidhatayn), for you will never recite anything like them."