وَسُيِّرَتِ الْجِبَالُ فَكَانَتْ سَرَابًا ﴿٢٠﴾

And the mountains shall be moved away from their places and they will be as if they were a mirage. This is similar to Allah's statement,

وَتَرَى الْجِبَالَ تَحْسَبُهَا جَامِدَةً وَهِىَ تَمُرُّ مَرَّ السَّحَابِ

And you will see the mountains and think them solid, but they shall pass away as the passing away of the clouds. (27:88)

He also says,

وَتَكُونُ الْجِبَالُ كَالْعِهْنِ الْمَنفُوشِ

And the mountain will be like carded wool. (101:5)

And Allah says here, فَكَانَتْ سَرَابًاً (As if they were a mirage.)

meaning, they appear to the one who looks at them as if they are something, but they are actually nothing. After this they will be completely removed. Nothing will be seen of them, and there will be neither base nor trace of them.

This is as Allah says,

وَيَسْـَلُونَكَ عَنِ الْجِبَالِ فَقُلْ يَنسِفُهَا رَبِّى نَسْفاً

فَيَذَرُهَا قَاعاً صَفْصَفاً

لاَّ تَرَى فِيهَا عِوَجاً وَلا أَمْتاً

And they ask you concerning the mountains, say:

"My Lord will blast them and scatter them as particles of dust. Then He shall leave them as a level smooth plain. You will see therein nothing crooked or curved.'' (20:105-107)

And He says,

وَيَوْمَ نُسَيِّرُ الْجِبَالَ وَتَرَى الاٌّرْضَ بَارِزَةً

And the Day We shall cause the mountains to pass away, and you will see the earth as a leveled plain. (18:47)