An-Nahl 16:105

قُلْ نَزَّلَهُ رُوحُ الْقُدُسِ مِن رَّبِّكَ بِالْحَقِّ لِيُثَبِّتَ الَّذِينَ آمَنُوا وَهُدًى وَبُشْرَىٰ لِلْمُسْلِمِينَ

Say, [O Muhammad], "The Pure Spirit has brought it down from your Lord in truth to make firm those who believe and as guidance and good tidings to the Muslims."

وَلَقَدْ نَعْلَمُ أَنَّهُمْ يَقُولُونَ إِنَّمَا يُعَلِّمُهُ بَشَرٌ ۗ لِّسَانُ الَّذِي يُلْحِدُونَ إِلَيْهِ أَعْجَمِيٌّ وَهَـٰذَا لِسَانٌ عَرَبِيٌّ مُّبِينٌ

And We certainly know that they say, "It is only a human being who teaches the Prophet." The tongue of the one they refer to is foreign, and this Qur'an is [in] a clear Arabic language.

إِنَّ الَّذِينَ لَا يُؤْمِنُونَ بِآيَاتِ اللَّهِ لَا يَهْدِيهِمُ اللَّهُ وَلَهُمْ عَذَابٌ أَلِيمٌ

Indeed, those who do not believe in the verses of Allah - Allah will not guide them, and for them is a painful punishment.

مَن كَفَرَ بِاللَّهِ مِن بَعْدِ إِيمَانِهِ إِلَّا مَنْ أُكْرِهَ وَقَلْبُهُ مُطْمَئِنٌّ بِالْإِيمَانِ وَلَـٰكِن مَّن شَرَحَ بِالْكُفْرِ صَدْرًا فَعَلَيْهِمْ غَضَبٌ مِّنَ اللَّهِ وَلَهُمْ عَذَابٌ عَظِيمٌ

Whoever disbelieves in Allah after his belief... except for one who is forced [to renounce his religion] while his heart is secure in faith. But those who [willingly] open their breasts to disbelief, upon them is wrath from Allah, and for them is a great punishment;

ذَٰلِكَ بِأَنَّهُمُ اسْتَحَبُّوا الْحَيَاةَ الدُّنْيَا عَلَى الْآخِرَةِ وَأَنَّ اللَّهَ لَا يَهْدِي الْقَوْمَ الْكَافِرِينَ

That is because they preferred the worldly life over the Hereafter and that Allah does not guide the disbelieving people.

أُولَـٰئِكَ الَّذِينَ طَبَعَ اللَّهُ عَلَىٰ قُلُوبِهِمْ وَسَمْعِهِمْ وَأَبْصَارِهِمْ ۖ وَأُولَـٰئِكَ هُمُ الْغَافِلُونَ

Those are the ones over whose hearts and hearing and vision Allah has sealed, and it is those who are the heedless.