Praise be to Allah.
Does swearing break your fast?
Committing sins during the day in Ramadan, such as swearing or insulting others, does not invalidate the fast as such, but it detracts from the reward for fasting. These sins may take away all of the reward, and the fasting person is left with nothing as a result of his fast apart from hunger and thirst.
Purpose of fasting in Islam
The fasting person is enjoined to guard all his faculties against disobeying Allah. The purpose behind fasting is not simply to refrain from eating and drinking, rather the purpose is to refrain from disobeying Allah and to achieve piety or fear of Allah. Allah says (interpretation of the meaning):
“O you who believe! Observing As-Sawm (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqun (the pious.)” [al-Baqarah 2:183]
The Prophet (peace and blessings of Allah be upon him) said: “Whoever does not give up false speech and acting upon it, Allah has no need of his giving up his food and drink.” (Narrated by al-Bukhari, 1903, 6075)
How to respond to insults while fasting
And the Prophet (peace and blessings of Allah be upon him) said: “If any one of you is fasting, let him not utter obscenities or act in an ignorant manner, and if anyone insults him or wants to fight him, let him say, I am fasting.” (Narrated by al-Bukhari, 1894; Muslim 1151)
“Let him not utter obscene speech” means let him not say any foul words.
“Let him not act in an ignorant manner” means let him not do any of the actions done by ignorant people such as yelling, being foolish, etc.
What is meant by this hadith is that he should not react in kind, rather he should limit himself to saying, ‘I am fasting.’”
If the fasting person is commanded not to react to one who insults him, how can it be appropriate for him to mistreat people or be the first to insult them?
Prohibition against obscene speech: Only in Ramadan?
“Note that the prohibition against obscene speech, ignorant action, argument and insults on the part of one who is fasting is not restricted only to him, rather each of these things is forbidden in general, but the prohibition is stronger in the case of one who is fasting.”
Al-Hakim narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Fasting does not just mean abstaining from food and drink, rather fasting means abstaining from idle and obscene speech. If someone curses you or treats you in an ignorant manner, then say, ‘I am fasting, I am fasting.’”
Ibn Majah (1690) said: Abu Hurayrah said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “It may be that the fasting person gets nothing from his fast apart from hunger, and it may be that the one who prays qiyam at night may get nothing from his qiyam but a sleepless night.”
And Allah knows best.