Surah Al-Hajj, Verse 47
وَيَسْتَعْجِلُونَكَ بِٱلْعَذَابِ وَلَن يُخْلِفَ ٱللَّهُ وَعْدَهُۥ ۚ وَإِنَّ يَوْمًا عِندَ رَبِّكَ كَأَلْفِ سَنَةٍۢ مِّمَّا تَعُدُّونَ
Translation — Sahih International
And they urge you to hasten the punishment. But Allah will never fail in His promise. And indeed, a day with your Lord is like a thousand years of those which you count.
Source
Kur'an-ı Kerim, Hac Suresi 22:47
https://kuran.diyanet.gov.tr/mushaf/kuran-meal-2/22-suresi-47-ayet