Commentary
Using foul or harsh language is not correct, even against infidels
The first verse (53) prohibits Muslims from talking harshly to disbelievers. It means that a hard line should not be taken unnecessarily, and should there be the need, even killing would be in order - as succinctly put in two lines of Persian poetry:
کہ بےحکم شرع آب خوردن خطاست وگر خون بفتوٰی بریزی رواست
Whereas, without an injunction of the Shari` ah, to drink water is a sin,
In another case, to shed blood under Fatwa is permissible!
Since it is possible to suppress the aggressive might of disbelievers and their hostility to Islam through fighting and killing (as an inevitable measure of defense), therefore, it is allowed. However, by using foul language and harsh words, neither a castle stands conquered nor anyone guided right, therefore, it has been prohibited. Imam al-Qurtubi said that this verse was revealed in the background of an event relating to Sayyidna ` Umar ؓ . It so happened that someone used foul language against Sayyidna ` Umar ؓ who retaliated harshly and wanted to kill him. This posed the danger of a war breaking out between their two tribes. Thereupon, this verse was revealed.
And according to the interpretation of Imam al-Qurtubi, this verse contains a guideline for Muslims as to how they should address each other. It suggests that they should not speak harshly at the time of mutual difference, for this is a trap door through which the Shaitan pushes them into mutual infighting and disorder.
Allah commands His servant Muhammad () to tell the believing servants of Allah that they should address one another in their conversations and discussions with the best and politest of words, for if they do not do that, Shaytan will sow discord among them, and words will lead to actions, so that evil and conflicts and fights will arise among them. For Shaytan is the enemy of Adam and his descendants, and has been since he refused to prostrate to Adam. His enmity is obvious and manifest. For this reason it is forbidden for a man to point at his Muslim brother with an iron instrument, for Shaytan may cause him to strike him with it. (Imam Ahmad recorded that Abu Hurayrah said: "The Messenger of Allah said:
(No one of you should point at his brother with a weapon, for he does not know whether Shaytan will cause him to strike him with it and thus be thrown into a pit of Fire.) Al-Bukhari and Muslim recorded this Hadith with the chain of narration from `Abdur-Razzaq.