Overall meaning : Allah Almighty describes some of the horrors of the Day of Resurrection, saying: Mention to the people, Messenger, the time when the sky will split open with emerging thin white clouds on the Day of Resurrection, and the angels will be sent down to the Place of Gathering—the plains of Judgement Day—in successive ranks. True authority and sovereignty on that Day will belong only to the All-Merciful God, not to earthly kings. It will be a hard day for the unbelievers.
He further mentions the intense regret the unbelievers will show on that day: And mention to them, Muhammad, the day when the wrongdoer who opposes Allah and His Messenger will bite at his hands in despair and regret, he says, ‘Woe betide me! If only I had followed the path of truth that the Messenger, showed us and had followed what he brought from his Lord. Alas for me! If only I had not taken so-and-so who had led me astray in the worldly life for a friend! He led me away from the Qur’an and right guidance after it had reached me.’ Allah then declares: Satan is ever treacherous to people who follow him, for he deserts him and lets him down when he most needs assistance and support.