Walillahi ghaybu assamawati wal-ardi wama amru assaAAati illa kalamhi albasari aw huwa (surah Nahl: 77)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(16:77) Allah alone has the knowledge of all the "unknown" things of the heavens and the earth. *70 As regards the coming of the Resurrection, it will not take more time than is taken in the twinkling of an eye rather less than this; *71 the fact is that Allah has power over all things.

Wa lillaahi ghaibus samaawaati wal ard; wa maaa amrus Saa`ati illaa kalamhil basari aw huwa aqrab; innal laaha `alaaa kulli shai`in Qadeer

*70) The subsequent sentence shows that this is the answer w a question which was frequently put to the Holy Prophet by the disbelievers of Makkah. The question which has not been cited was this: If the Resurrection you so often talk of is really coming, Iet us know the date of its coming.
*71) That is, "Don't be under the delusion that the Resurrection will come gradually and take a long time: you will neither be able to sec it coming at a distance nor guard against it and make preparations to meet it. For it will come suddenly without any previous notice, in the twinkling of an eye or even take less time than this. Therefore, now is the time to consider this matter seriously and to decide about your attitude towards it. You should not depend upon this false hope that there is still a long time in the coming of the Resurrection and you will set matters right with Allah when you will see it coming" .
It may be pointed out that the Resurrection has been mentioned here during the discussion on Tauhid in order to warn the people that the choice between the doctrines of Tauhid and shirk is not merely a theoretical question. For that choice determines different courses of life for which they will be called to account on the Day of Resurrection. They have also been warned that it will come aII of a sudden at some unknown time. Therefore, they should be very careful to make that choice which will determine their success or failure on that Day.