Question: In Ramadaan, is the Sawm (Fast) of a person, who, while in a rage, reviles or swears at another, invalidated by doing so?
Answer: Doing so does not invalidate Sawm, but it does detract from its reward. Muslims should control themselves and guard their tongue against swearing, reviling, backbiting, gossiping and other things forbidden by Allaah whether or not they are fasting. However, a Muslim, while observing Sawm, should be all the more keen to preserve the integrity of their Sawm and be more watchful against anything offensive or may sow the seeds of discord and disunity among people, because the Prophet (peace be upon him) said: When any of you is observing Sawm on a day, they should neither speak bad words nor raise their voice. If anyone reviles them or tries to quarrel with them, they should say: ‘I am fasting.’ (Agreed upon by Al-Bukhaaree and Muslim.).. read more here.