The Messenger of Allah ﷺ said, "Allah the Exalted said to me, 'Your nation will continue to question one another until they say, "This is Allah who created mankind, but who created Allah?"'"
حدثنا محمد بن فضيل عن المختار بن فلفل
قال رسول الله ﷺ إن الله تعالى قال لي إن أمتك لا يزالون يتساءلون فيما بينهم حتى يقولوا هذا الله خلق الناس فمن خلق الله
Its isnad is sahih, it was mentioned before in similar wording under 1359.