Alsiraj Official Website
Sayings (Hadiths) of Prophet Muhammad
About the obligation of curbing the fasting person's tongue
Narrated Abu-Huraira: Allah's Messenger said: observing fast is a shield (or a screen or a shelter from Hellfire). So a person observing a fast should avoid sexual acts and should not behave foolishly and impudently, and is someone quarrels with or abuses him, he should say to him twice: I am observing fasting. The Prophet added: By Him in Whose Hands my soul is, the smell coming from the mouth of a person observing fasting is better to Allah than the smell of musk.
Allah says about the fasting person: (he has left his food, drink, and desires for My sake. Fasting is for Me. So I will reward the fasting person for it and the reward of good deeds is multiplied ten times.)
(Bukhari)
Narrated Abu-Huraira: the Prophet said: whoever does not give up lying speech(false statements) and acting on those lies and evil actions, etc. Allah is not need of his leaving his food and drink(Allah will not accept his fasting).
(Bukhari)