Narrated Abu Hurairah (ra),
The Prophet (pbuh) said that:
“Your # Lord said, Every ( # sinful ) deed can be expiated; and As-Sawn (the fasting) is for Me; so I will give the # reward for it; and the smell which comes out of the mouth of a fasting person, is better with # Allah than the smell of # musk .” Sahih Al-Bukhari, Volume No.9
The Book of Tauheed, Hadith No. 7538.