But those who disbelieve will not cease to be in doubt of it until the Hour comes upon them unexpectedly or there comes to them the punishment of a barren Day.1
Translation: Saheeh International (English)
1 One which will not be followed by night and therefore will not give birth to a new day, referring to the Day of Resurrection.
Those who disbelieved in Allah and denied His Messenger will remain in doubt about the Qur’ān Allah revealed to you, continuing until the Hour comes to them suddenly whilst they are in that condition or the punishment of a day in which there is no mercy or good comes to them, and it is the Day of Judgment with respect to them.