Musnad Abu Ya'la al-Mawsili 42:284

Zuhayr narrated to us, Yunus ibn Muhammad narrated to us, Layth narrated to us, from Yazid ibn al-Had, from Suhayl ibn Abi Salih, from al-Nu’man ibn Abi ‘Ayyash, from Abu Sa’id al-Khudri, that he heard the Messenger of Allah (may Allah bless him and grant him peace) saying: "There is no servant who fasts a day in the way of Allah, except that Allah distances his face by that day from the Fire [a distance of] seventy autumns."