Ayyub bin Hibban al-Wasiti narrates: I heard a man ask Sufyan bin Uyaynah (may Allah have mercy on him): "O Abu Muhammad, (what about) the report which the Prophet (peace and blessings be upon him) narrates from his Lord: 'Every deed of the son of Adam is for him except fasting, for it is for Me and I will give its reward'?" Ibn Uyaynah said: "This is among the finest and wisest of hadiths. When the Day of Resurrection comes, Allah, Mighty and Majestic, will take account of His servant and settle the wrongs he owes from all his other deeds, until nothing remains but fasting. Then Allah will bear whatever wrongs remain against him and admit him to Paradise because of fasting."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8335