Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Every deed of the son of Adam is multiplied, a good deed from ten times up to seven hundred times. Allah, Mighty and Majestic, said: Except fasting, for it is for Me and I Myself will give its reward; he leaves his desire and his food and drink for My sake. The fasting person has two joys: one joy at the time of breaking the fast and the other at the time of meeting his Lord. And the smell of the fasting person's mouth is more pleasant and fragrant to Allah than the fragrance of musk. Fasting is a shield, fasting is a shield."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8332