Tafsir of An-Nazi'at 79:7

(Followed by the succeeding one): That is, the one that stands or the blast that follows and succeeds the first one, which is the second blast. It is also said that it refers to the succeeding celestial bodies, namely the sky and the stars, for they split and scatter afterward.

The clause is in the state (hal) of the first blast (al-rajifah), validating the use of "the Day" as a temporal adverb for the Resurrection, as it conveys the extension and breadth of the time. This is because it indicates that the Day is the timeframe of the first blast, which is qualified by the second blast succeeding it. Since the succession of one thing to another presupposes the existence of the former, the "Day" must necessarily extend until the second blast.

Even though the Resurrection does not occur at the second blast—given that there are forty [years/units of time] between it and the first—it is considered in terms of its extension to emphasize the terror of the Day by clarifying that it is the site of two momentous calamities.

It is also said that "the Day when the blast shakes" is governed by an implied verb, "Remember." Thus, the clause is an inception (isti'naf) confirming the content of the omitted response, as if it were said to the Messenger of Allah, peace be upon him: "Remind them of the day of the two blasts, for it is the time of their resurrection." It is also said that it is governed by what is indicated by the saying of the Almighty...