“The Day the earth will shake,” meaning: that shall be for them on the Day when the earth shakes, i.e., it trembles, “and the mountains,” and it will be, meaning: it will become, that is: “the mountains as a heap of sand,” meaning: sand, “poured forth,” meaning: flowing.
﴿يَوْم ترجف الأَرْض﴾ أَيْ: ذَلِكَ لَهُمْ يَوْمَ تَرْجُفُ الأَرْض تتزلزل ﴿وَالْجِبَال وَكَانَت﴾ أَيْ: وَصَارَتْ؛ يَعْنِي: ﴿الْجِبَالُ كَثِيبًا﴾ أَي: رملاً ﴿مهيلا﴾ أَي: سَائِلًا
