صحيح مسلم

Abu Huraira reported Allah's Messenger (ﷺ) as saying: Allah the Exalted and Majestic said: Every act of the son of Adam is for him, except fasting. It is (exclusively) meant for Me and I (alone) will reward it. Fasting is a shield. When any one of you is fasting on a day, he should neither indulge in obscene language, nor raise the voice; or if anyone reviles him or tries to quarrel with him he should say: I am a person fasting. By Him, in Whose Hand is the life of Muhammad, the breath of the observer of fast is sweeter to Allah on the Day of judgment than the fragrance of musk. The one who fasts has two (occasions) of joy, one when he breaks the fast he is glad with the breaking of (the fast) and one when he meets his Lord he is glad with his fast.