Narrated Abu Huraira:
Allah's Apostle said, "Fasting is a shield (or a screen or a shelter).
So, the person observing fasting should avoid sexual relation with his
wife and should not behave foolishly and impudently, and if somebody
fights with him or abuses him, he should tell him twice, 'I am
fasting." The Prophet added, "By Him in Whose Hands my soul is, the
smell coming out from the mouth of a fasting person is better in the
sight of Allah than the smell of musk. (Allah says about the fasting
person), 'He has left his food, drink and desires for My sake. The fast
is for Me. So I will reward (the fasting person) for it and the reward
of good deeds is multiplied ten times."
(Sahih Al-Bucharyy)