Sahih Muslim
The Book of Fasting (Kitab Al-Sawm)
Book Number: 006 / Hadith Number: 2573
Abu Sa'id al-Khudri (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) 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.