Narrated Abu Huraira:

The Prophet ﷺ said that your Lord said, "Every (sinful) deed can be expiated;
and the fast is for Me, so I will give the reward for it;
and the smell which comes out of the mouth of a fasting person, is better in Allah's Sight than the smell of musk." (See Hadith No. 584)

حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا مُحَمَّدُ بْنُ زِيَادٍ، قَالَ سَمِعْتُ أَبَا هُرَيْرَةَ، عَنِ النَّبِيِّ ﷺ يَرْوِيهِ عَنْ رَبِّكُمْ، قَالَ " لِكُلِّ عَمَلٍ كَفَّارَةٌ، وَالصَّوْمُ لِي وَأَنَا أَجْزِي بِهِ، وَلَخَلُوفُ فَمِ الصَّائِمِ أَطْيَبُ عِنْدَ اللَّهِ مِنْ رِيحِ الْمِسْكِ ".