It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: The reward of a good deed is ten times. Allah Almighty has said: Fasting is for Me and I Myself will give its reward. The fasting person leaves his food and drink for My sake, therefore fasting is for Me and I Myself will give its reward. The breath of the fasting person’s mouth is more pleasant to Allah than the fragrance of musk.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10691