It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "When it is the day of fasting for any of you, he should not speak obscenely nor behave ignorantly (rudely); and if someone behaves ignorantly (rudely) towards him, he should say: I am fasting." And the Messenger of Allah (peace and blessings be upon him) said: "Allah, the Mighty and Majestic, says: Fasting is for Me, and it is I who will reward it." "And for the fasting person there are two joys: a joy on the day he meets his Lord, and a joy at the time of breaking his fast," and the smell of the fasting person's mouth is more pleasing to Allah than the fragrance of musk.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10161