﴿وَيَسْـَلُونَكَ عَنِ الْجِبَالِ﴾
(And they ask you concerning the mountains.) This is a question, will they remain on the Day of Resurrection or will they cease to exist
﴿فَقُلْ يَنسِفُهَا رَبِّى نَسْفاً﴾
(Say: "My Lord will blast them and scatter them as particles of dust.'') This means that He will take them away from their places, wipe them out and remove them completely.
(Then He shall leave it) referring to the earth;
(as a level smooth plain.) This means one expanse spread out. The word Qa` means a piece of land that is level and the word Safsafa is used to place emphasis on this meaning. It has also been said that Safsafa means that which has no vegetation growing in it. The first meaning is preferred, even though the second meaning is also included by necessity. In reference to this, Allah says,
﴿لاَّ تَرَى فِيهَا عِوَجاً وَلا أَمْتاً ﴾
(You will see therein no crookedness nor curve. ) meaning, `on that Day you will not see in the earth any valley, hill, or any place, whether low or elevated.' Ibn `Abbas, `Ikrimah, Mujahid, Al-Hasan Al-Basri, Ad-Dahhak, Qatadah and others of the Salaf all said the same.