It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) as a marfu' report: "Allah, the Mighty and Majestic, says: Fasting is for Me, and I Myself will reward it. And the fasting person has two joys: a joy at the time of breaking his fast, and a joy when he meets his Lord. And the odour of the fasting person's mouth is more pleasing to Allah than the fragrance of musk."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10042