Prophet Muhammad (s.a.w.) said:
"Whoever backbites his Muslim brothers, his fasting will be invalid and his ablution null. Should he die in such a state, he will die like the one who decreed lawful what Allah has forbidden."
Imam Ali, Ameer al Mu'mineen (a.s.) quotes the Holy Prophet (s.a.w.) for saying:
"Whoever fasts during the month of Ramadhan out of faith and seeking Allah's pleasure and guards his ears, eyes and tongue from harming people, Allah will accept his fasting, forgive his past sins. . ."
Imam Muhammad al Baqir (a.s.) said to Jabir ibn Abdullah:
"O Jabir, whoever, fasts the days of Ramadhan, stands for prayers in parts of its nights, guards his/her sexual desires, reins in his/her tongue, lowers his/her gaze and injures, not the feelings of others, will become free of sins as on the day he/she was born."
Imam Jafar al Sadiq (a.s.) said:
"If a fasting person when abused, replies peace be upon you I will not abuse as you do, the Lord, the Exalted and Most High says, By fasting, My servant has saved himself from the evil of My other servant, I grant him refuge against the fire."
Imam Jafar al Sadiq (a.s.) says:
"When you fast, guard your hearing and sight against the forbidden, and your limbs and all other organs from the vile. Do not rave at or injure a servant. Be dignified as a fasting person should, and keep silent and calm, except when remembering Allah. Do not regard your fasting day as an ordinary day and refrain from intercourse, kissing and loud laughter, because Allah dislikes that."
Imam Jafar al Sadiq (a.s.) said:
"Allah made fasting incumbent to make equity between the rich and the poor. A rich man does not feel the pains of hunger to have mercy for the poor, since he is able to obtain whatever he likes. (By enjoining fasting) Allah wanted to put His creatures on an equal footing by making the rich taste the pain of hunger, so that he may pity the weak and have mercy on the hungry. . ."
Imam Ali al Reza (a.s.) said:
"O people, anybody who in this month cultivates good manners will walk over the Sirat (bridge to Paradise) on the day when feet will tend to slip. . ."
source : http://abna.ir