The Prophet ﷺ said, "Allah says, 'Fasting is for Me, and I Myself reward it.' The one who fasts has two moments of joy. He rejoices when he breaks his fast, and he rejoices when he meets Allah and receives His reward. By the One in whose hand is Muhammad's soul, the breath from the mouth of the fasting person is more fragrant to Allah than the scent of musk."
أخبرنا علي بن حرب قال حدثنا محمد بن فضيل قال حدثنا أبو سنان ضرار بن مرة عن أبي صالح
قال النبي ﷺ إن الله تبارك وتعالى يقول الصوم لي وأنا أجزي به وللصائم فرحتان إذا أفطر فرح وإذا لقي الله فجزاه فرح والذي نفس محمد بيده لخلوف فم الصائم أطيب عند الله من ريح المسك
Muslim narrated it in Kitab al-Siyam, chapter on the merit of fasting, no. 165/1151, from the hadith of Muhammad bin Fudayl bin Ghazwan, with this wording. It is also in Kubra, no. 2523.