"My coming and the Hour are like these two," and he separated his middle finger from the one next to the thumb.Then he said, "My coming and the Hour are like two racehorses."Then he said, "My coming and the Hour are like a man whose people sent him ahead as a scout. When he feared he would be overtaken, he waved his garment, signaling, 'You are about to be attacked! You are about to be attacked!'"Then the Messenger of Allah ﷺ would say, "I am that man."
و قال أبو حازم قال رسول الله ﷺ قال أبو ضمرة لا أعلمه إلا
مثلي ومثل الساعة كهاتين وفرق بين أصبعيه الوسطى والتي تلي الإبهام ثم قال مثلي ومثل الساعة كمثل فرسي رهان ثم قال مثلي ومثل الساعة كمثل رجل بعثه قومه طليعة فلما خشي أن يسبق ألاح بثوبه أتيتم أتيتم ثم يقول رسول الله ﷺ أنا ذلك
Its isnad is sahih. It was also mentioned briefly earlier at 22695.