The Messenger of Allah ﷺ said, "The Hour will not come until no one on earth says, 'Allah, Allah.'"
حدثنا ابن أبي عدي عن حميد
قال رسول الله ﷺ لا تقوم الساعة حتى لا يقال في الأرض الله الله
Its isnad is sahih. Muslim narrated it, 1/131, no. 148, in the Book of Faith, chapter on the disappearance of faith, and Tirmidhi, 4/492, no. 2207, in the Book of Tribulations, chapter on the signs of the Hour, and he graded it hasan.