Reported in verse 7: وَقَالَ الَّذِينَ كَفَرُوا هَلْ نَدُلُّكُمْ عَلَىٰ رَجُلٍ يُنَبِّئُكُمْ إِذَا مُزِّقْتُمْ كُلَّ مُمَزَّقٍ إِنَّكُمْ لَفِي خَلْقٍ جَدِيدٍ (Shall we point out to you a man...). There is a statement of disbelievers who denied the coming of Qiyamah. In an exercise of mockery, they used to say, 'come, let us identify an unusual person for your benefit, a person who loves to tell you how, when you die and become dust, totally powdered into countless particles, even after all that, you will be brought into a new creation - and that you, all reshaped into the form you once were, will be made to stand up alive!'
It is obvious that the person alluded to here is no other but the Holy Prophet ﷺ who used to tell people that Qiyamah will come when the dead will become alive once again, and exhorted people to put their faith in it. All these people who were deriding him knew him perfectly well, but in the present context, they have mentioned him in a manner as if they knew nothing else about him - nothing else but that he tells people about the dead rising alive on the day of Qiyamah. They had purposely elected to refer to him in that manner just to mock and deride him.
The word: مُزِّقْتُمْ (when you are totally torn into pieces) is a derivation from: مزقِ (mazq) which means splitting apart and rendering to pieces, and: كُلَّ مُمَزَّقٍ (kulla mumazzaq: (totally torn) means the disintegration of the human body in a manner that all its particles get dispersed separately. Onwards from here, they take up another mode to comment on his statement relating to the Qiyamah.