Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Allah says, 'O son of Adam! Every deed is an expiation except for fasting; it (fasting) is for Me and I alone will reward it. The smell from the mouth of the fasting person is better with Allah than the fragrance of musk.'"
Hadith Referenceمسند اسحاق بن راهويه / كتاب الصوم / 403
Hadith Takhrij«بخاري ، كتاب التوحيد ، باب ذكر النبى صلى الله عليه واله وسلم الخ ، رقم : 7538 . مسلم ، كتاب الصيام ، باب فضل الصيام ، رقم : 1151 . سنن نسائي ، رقم : 2211 . مسند احمد : 393/2 .»
Muhammad bin Ziyad narrated, I heard Abu Huraira (may Allah be pleased with him) narrate the same example from the Prophet Muhammad (peace and blessings be upon him).
Hadith Referenceمسند اسحاق بن راهويه / كتاب الصوم / 404