Juray bin Kulayb narrates from Sayyiduna Bashir bin al-Khasasiyah (may Allah be pleased with him), and our companions also told us from Sayyiduna Abu Hurayrah (may Allah be pleased with him), that the Prophet (peace and blessings be upon him) said, narrating from his Lord, the Exalted: "Fasting is a shield by which My servant shields himself from the Fire. Fasting is for Me, and I Myself will reward it; he leaves his food and his desire for My sake. By the One in whose hand is my soul, the smell of the fasting person's mouth is, with Allah, the Mighty and Majestic, on the Day of Resurrection, better than the fragrance of musk."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1224