An-Naba 78:1 - Linguistic Miracle

Regarding what are they asking each other?

The speaker is Allah Himself and this question is not of genuine inquiry, but rather it is phrased as such to disapprove the manner in which they are questioning each other because these people are not asking it out of genuine curiosity or need, rather they do so mockingly.¹ We experience this in our daily lives as well. When someone says something that people do not take kindly to, more often than not their response is, “Did you really just say that?” They are not asking the speaker if he actually said it - he obviously did, they are just mocking him.

Secondly, it could be that they are debating this topic with each other, with some of them mockingly mentioning it to others as a way of pastime, but it could also be that they are directing their mockery at the prophet ﷺ and the believers.²

This surah centers around judgment day and the doubts expressed by people about its authenticity. Allah will use the concept of zawj - the fact that every object has an equal, yet opposite counterpart to prove its authenticity in a most unusual manner.

¹ al-Ālūsī, Rūḥ al-Maʿānī, vol. 28, p. 197
² al-Ālūsī, Rūḥ al-Maʿānī, vol. 28, p. 198; Ibn ʿĀshūr, al-Taḥrīr wa al-Tanwīr, vol. 30, p. 8