Overall meaning : The Almighty says: On the day Allah gathers the unbelievers together on the Plain of Gathering for the final judgement, it will seem to them as if they had stayed in the worldly life no longer than an hour of a day, getting to know one another as they used to do in the life of the world. Those who denied the meeting with Allah will then lose Allah’s reward and Paradise; they were not in the slightest guided to the truth for having denied the resurrection and life after death.
Whether We let you, Muhammad, witness the unbelievers’ punishment during your lifetime by hastening it for them, or We cause you to die before it befalls them, still to Us will they be returned. Allah is witness to all their actions, and He will repay them according to what they have done.
The Almighty then states that He has sent a messenger to every nation to call them to faith and to worship Him alone; and that when their messenger comes on Judgement Day to bear witness that he has conveyed His message to them, Allah will judge between them with absolute justice and will not wrong them at all.