Then Allah says,

لِأَيِّ يَوْمٍ أُجِّلَتْ ﴿١٢﴾

لِيَوْمِ الْفَصْلِ ﴿١٣﴾

وَمَا أَدْرَاكَ مَا يَوْمُ الْفَصْلِ ﴿١٤﴾

وَيْلٌ يَوْمَئِذٍ لِّلْمُكَذِّبِينَ ﴿١٥﴾

For what Day are these signs postponed?

For the Day of Sorting Out.

And what will explain to you what is the Day of Sorting Out?

Woe that Day to the deniers!

Allah is saying, `for which day are the Messengers postponed and their matter expected, so that the Hour will be established.'

This is as Allah says,

فَلاَ تَحْسَبَنَّ اللَّهَ مُخْلِفَ وَعْدِهِ رُسُلَهُ إِنَّ اللَّهَ عَزِيزٌ ذُو انتِقَامٍ

يَوْمَ تُبَدَّلُ الاٌّرْضُ غَيْرَ الاٌّرْضِ وَالسَّمَـوَتُ وَبَرَزُواْ للَّهِ الْوَاحِدِ الْقَهَّارِ

So think not that Allah will fail to keep His promise to His Messengers. Certainly, Allah is Almighty, All-Able of Retribution.

On the Day when the earth will be changed to another earth and so will be the heavens, and they will appear before Allah, the One, the Irresistible. (14:47, 48)

This is the Day of Sorting Out, as Allah says,

لِيَوْمِ الْفَصْلِ

the Day of Sorting Out.

Then Allah says, in magnifying its matter,

وَمَا أَدْرَاكَ مَا يَوْمُ الْفَصْلِ

وَيْلٌ يَوْمَئِذٍ لِّلْمُكَذِّبِينَ

And what will explain to you what is the Day of Sorting Out?

Woe that Day to the deniers.

meaning, woe unto them from Allah's torment that is coming in the future.