Narrated Abu Huraira: The Prophet (sallallaahu alaihi wa sallam), 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 or impudently, and if somebody fights with or abuses him, he should tell him twice, ‘I am fasting”.

The Prophet added,

“By Him in Whose Hands me soul is, the smell coming out of 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 goods deeds is multiplied ten times.”

(Sahih Al-Bukhari)