Sahih Bukhari Volume 9, Book 97, Hadith 7494

حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا الأَعْمَشُ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ يَقُولُ اللَّهُ عَزَّ وَجَلَّ الصَّوْمُ لِي وَأَنَا أَجْزِي بِهِ يَدَعُ شَهْوَتَهُ وَأَكْلَهُ وَشُرْبَهُ مِنْ أَجْلِي، وَالصَّوْمُ جُنَّةٌ، وَلِلصَّائِمِ فَرْحَتَانِ فَرْحَةٌ حِينَ يُفْطِرُ وَفَرْحَةٌ حِينَ يَلْقَى رَبَّهُ، وَلَخَلُوفُ فَمِ الصَّائِمِ أَطْيَبُ عِنْدَ اللَّهِ مِنْ رِيحِ الْمِسْكِ ‏"‏‏

Narrated By Abu Huraira : The Prophet said, "Allah said: The Fast is for Me and I will give the reward for it, as he (the one who observes the fast) leaves his sexual desire, food and drink for My Sake. Fasting is a screen (from Hell) and there are two pleasures for a fasting person, one at the time of breaking his fast, and the other at the time when he will meet his Lord. And the smell of the mouth of a fasting person is better in Allah's Sight than the smell of musk."