Al-Jathiyah 45:32

Wa-itha qeela inna waAAda Allahihaqqun wassaAAatu la rayba feehaqultum ma nadree ma assaAAatu in nathunnuilla thannan wama nahnubimustayqineen

And when it was said, 'Indeed, the promise of Allāh is truth and the Hour [is coming] - no doubt about it,' you said, 'We know not what is the Hour. We assume only assumption, and we are not convinced.'"

and when it was said to you that Allah’s promise is true and there is no doubt in the (arrival of the) Hour, you used to say, ‘We do not know what the Hour is. We do not think (about it) but as an assumption, and we are not sure.’”