In the last verse (73): جَاهِدِ الْكُفَّارَ‌ وَالْمُنَافِقِينَ وَاغْلُظْ عَلَيْهِمْ (carry out Jihad against the disbelievers and hypocrites and be strict with them), the Holy Prophet ﷺ has been commanded to wage Jihad against disbelievers and hypocrites both and to be strict in their case. The need to fight against belligerent disbelievers is self-evident. But, the meaning of carrying out Jihad against the hypocrites is explained by the very conduct of the Holy Prophet ﷺ . It proves that Jihad against them signifies vocal Jihad through which they should be induced to understand the veracity of Islam, start to feel for it and thus become sincere in their adherence to Islam. (Qurtubi and Mazhari) Please bear in mind that the real meaning of the word: غلظ (ghilaz) used in: واَغلظ (and be strict with them) is that one should not show any leniency or grant any concessions in taking a course of action which the person ad-dressed deserves. This word is used as an antonym to رأفۃ (ra'fah) which means mercy and kindheartedness.

In his comments, Imam al-Qurtubi has said that the use of the word: ghilzah (strictness) at this place means that leniency should not be shown and concessions should not be granted when the injunctions of Sharl'ah are enforced on them. This approach has nothing to do with being vocally strict - because, that is against the favored practice of the blessed prophets. They are never harsh in speech, nor do they curse and swear. In Hadith, the Holy Prophet ﷺ is reported to have said: اِذ ازَنَت اَمَۃُ اَحَدِکُم فَلیَجِلدُھَا الحَدّ ولا یُشَرِّب عَلَیھَا (If a bondwoman of anyone among you commits fornication, just enforce the Islamic legal punishment for it on her - but, do not denounce her verbally) (Qurtubi)

Alluding to the persona of the Holy Prophet ﷺ - the image he exuded in his presence before people - Allah Ta` ala has Himself said: وَلَوْ كُنتَ فَظًّا غَلِيظَ الْقَلْبِ لَانفَضُّوا مِنْ حَوْلِكَ (and had you been rough and hard hearted, they would have dispersed from around you - 3:159). Then, there is no evidence even from the actual dealings of the Holy Prophet ﷺ that he ever demonstrated any harsh attitude in conversation or address before disbelievers and hypocrites.

A warning signal

It is certainly a matter of regret that the attitude of harshness in address and conversation was something Islam never took to even against Kuffar, the rigid and hostile disbelievers. But, contemporary Muslims would not bat an eye and use it against other Muslims - not to say much about many of those who would congratulate themselves for having done this as some service to their religion. Innalillah ...