Sahih Muslim 148
Sahih Muslim · Book 1: The Book of Faith · The Disappearance of Faith at the End of Time
It is narrated on the authority of Anas that the Messenger of Allah (ﷺ) said:
حَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ ، أَخْبَرَنَا عَبْدُ الرَّزَّاقِ ، أَخْبَرَنَا مَعْمَرٌ ، عَنْ ثَابِتٍ ، عَنْ أَنَسٍ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ تَقُومُ السَّاعَةُ عَلَى أَحَدٍ يَقُولُ اللَّهُ اللَّهُ " .
"The Hour (Resurrection) will not occur as long as anyone says: 'Allah, Allah.'"