The Virtue of Fasting for in the cause of Allah, for those who are able to without suffering any harm or neglecting other duties Sahih Muslim 1153 c
Translation
Abu Sa'id al-Khudri (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying
He who observes fast for a day in the way of Allah He would remove his face from the Hell to the extent of seventy years' distance.