Musnad Ahmad 482:50

Hashim narrated to us, Layth narrated to us, Yazid ibn Abi Habib narrated to me, from Abu Imran Aslam, from Uqbah ibn Amir al-Juhani, that he said: I followed the Messenger of Allah, peace and blessings of Allah be upon him, while he was riding, and I placed my hand upon his feet, and I said: "Teach me from Surah Yusuf." He said: "You will never recite anything more eloquent in the sight of Allah than 'Say, I seek refuge in the Lord of the daybreak.'"