Sura al-Jāthiyah 45:32

وَإِذَا قِيلَ إِنَّ وَعْدَ ٱللَّـهِ حَقٌّ وَٱلسَّاعَةُ لَا رَيْبَ فِيهَا قُلْتُم مَّا نَدْرِى مَا ٱلسَّاعَةُ إِن نَّظُنُّ إِلَّا ظَنًّا وَمَا نَحْنُ بِمُسْتَيْقِنِينَ

wa-idhā qīla inna waʿda allāhi ḥaqqun wa-l-sāʿatu lā rayba fīhā qultum mā nadrī mā l-sāʿatu in naẓunnu illā ẓannan wa-mā naḥnu bimustayqinīna

"And when it was said that the promise of Allah was true, and that the Hour- there was no doubt about its (coming), ye used to say, 'We know not what is the hour: we only think it is an idea, and we have no firm assurance.'"