I saw the Messenger of Allah ﷺ gesture with his two fingers like this, the middle finger and the one next to the thumb, saying, "I was sent, and the Hour is like these two."
رأيت رسول الله ﷺ قال بأصبعيه هكذا بالوسطى والتي تلي الإبهام: بعثت والساعة كهاتين.
Bukhari related it in the Book of Tafsir (4936), and Muslim related it in the Book of Tribulations and Signs of the Hour (2950), both through routes from Abu Hazim, from Sahl bin Saad, as mentioned.As for His saying, "So how will they benefit from their reminder when it comes to them?", this means, from where would they be able to remember when the Hour comes to them? Its time has already passed and gone. This is similar to His saying, "That Day, man will remember, but what good to him will be the remembrance?" [Fajr 89:23]. Their faith, their remembrance, and their seeking to make amends will not benefit them at all on that day.