Reference: al-Bukhaaree – Volume 6, Page 35, Muslim – Number 1153
Abu Sa’eed al-Khudree (radhi-yAllaahu ‘anhu) narrated that the Messenger of Allaah ﷺ said:
There is not a servant who fasts a day in the way of Allaah, except that Allaah removes his face from the Fire by the distance of seventy years because of that.