Musnad Abu Ya'la al-Mawsili 107:34

Abu Hammam narrated to us, Muhammad ibn Shu'ayb ibn Shapur narrated to us, Abu 'Amr Yahya ibn al-Harith al-Dhimari informed me that he heard al-Qasim Abu 'Abd al-Rahman, the freed slave of Yazid ibn Mu'awiyah ibn Abi Sufyan, raising the hadith to 'Uqbah, from the Messenger of Allah (may Allah bless him and grant him peace), who said: "Whoever fasts one day in the way of Allah, Allah will distance Hell from him by a distance of one hundred years."