The Prophet ﷺ said, "The breath of the fasting person is more fragrant to Allah than the scent of musk. Your Lord says, 'My servant has left his desires, his food, and his drink seeking My pleasure. Fasting is for Me, and I am the one who rewards for it.'"
حدثنا هوذة حدثنا عوف بن أبي جميلة عن محمد
عن النبي ﷺ قال لخلوف فم الصائم أطيب عند الله من ريح المسك قال قال ربكم عز وجل عبدي ترك شهوته وطعامه وشرابه ابتغاء مرضاتي والصوم لي وأنا أجزي به
Its isnad is sahih. It was previously mentioned in 7485, and it is found in Bukhari 4/102 no. 1894 (Fath al-Bari), in the Book of Fasting, the merit of fasting, and in Muslim 2/807 no. 165, in the Book of Fasting, what has been said about the merit of fasting, and similarly in Tirmidhi 2/127 no. 764, and likewise in Nasai 4/164 no. 2218, and Ibn Majah has the same 1/525 no. 1638.