Musnad Ahmad 30:3045

Waki’ narrated to us, al-A’mash narrated to us, from Abu Salih, from Abu Hurairah; and ‘Abd al-Rahman narrated to us, from Sufyan, from al-A’mash, from Abu Salih, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Every deed of the son of Adam is multiplied; a good deed is ten times its like, up to seven hundred times, up to what Allah wills. Allah, the Mighty and Majestic, says: 'Except for fasting, for it is Mine, and I reward for it. He leaves his food and his drink for My sake.'" "And for the fasting person are two joys: a joy at the time of his breaking fast, and a joy at the time of meeting his Lord." "And the change in the breath of his mouth is better in the sight of Allah, the Mighty and Majestic, than the scent of musk. Fasting is a shield, fasting is a shield."