30:6
وَعْدَ ٱللَّهِ ۖ لَا يُخْلِفُ ٱللَّهُ وَعْدَهُۥ وَلَـٰكِنَّ أَكْثَرَ ٱلنَّاسِ لَا يَعْلَمُونَ
[It is] the promise of Allah. Allah does not fail in His promise, but most of the people do not know.
The Romans
وَعْدَ ٱللَّهِ ۖ لَا يُخْلِفُ ٱللَّهُ وَعْدَهُۥ وَلَـٰكِنَّ أَكْثَرَ ٱلنَّاسِ لَا يَعْلَمُونَ
[It is] the promise of Allah. Allah does not fail in His promise, but most of the people do not know.
Nearby ayahs help place verse 30:6 in sequence and meaning.
فِى بِضْعِ سِنِينَ ۗ لِلَّهِ ٱلْأَمْرُ مِن قَبْلُ وَمِنۢ بَعْدُ ۚ وَيَوْمَئِذٍ يَفْرَحُ ٱلْمُؤْمِنُونَ
Within three to nine years. To Allah belongs the command before and after. And that day the believers will rejoice
بِنَصْرِ ٱللَّهِ ۚ يَنصُرُ مَن يَشَآءُ ۖ وَهُوَ ٱلْعَزِيزُ ٱلرَّحِيمُ
In the victory of Allah. He gives victory to whom He wills, and He is the Exalted in Might, the Merciful.
يَعْلَمُونَ ظَـٰهِرًا مِّنَ ٱلْحَيَوٰةِ ٱلدُّنْيَا وَهُمْ عَنِ ٱلْـَٔاخِرَةِ هُمْ غَـٰفِلُونَ
They know what is apparent of the worldly life, but they, of the Hereafter, are unaware.
أَوَلَمْ يَتَفَكَّرُوا۟ فِىٓ أَنفُسِهِم ۗ مَّا خَلَقَ ٱللَّهُ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضَ وَمَا بَيْنَهُمَآ إِلَّا بِٱلْحَقِّ وَأَجَلٍ مُّسَمًّى ۗ وَإِنَّ كَثِيرًا مِّنَ ٱلنَّاسِ بِلِقَآئِ رَبِّهِمْ لَكَـٰفِرُونَ
Do they not contemplate within themselves? Allah has not created the heavens and the earth and what is between them except in truth and for a specified term. And indeed, many of the people, in [the matter of] the meeting with their Lord, are disbelievers.