Key Verses

1. 30:44Ar-RumWarning
   مَن كَفَرَ فَعَلَيۡهِ كُفۡرُهُۥۖ وَمَنۡ عَمِلَ صَٰلِحٗا فَلِأَنفُسِهِمۡ يَمۡهَدُونَ
   Whoso disbelieveth must (then) bear the consequences of his disbelief, while those who do right make provision for themselves -
   In context

   Whoever disbelieves in Allah, the harm of his disbelief - which is permanent residence in the hellfire - will reach only himself. As for those who do good deeds seeking Allah’s pleasure through them, they are preparing for themselves entry into paradise and deriving enjoyment from whatever is within it, and they shall live in it forever.

2. 31:23Luqman
   وَمَن كَفَرَ فَلَا يَحۡزُنكَ كُفۡرُهُۥٓۚ إِلَيۡنَا مَرۡجِعُهُمۡ فَنُنَبِّئُهُم بِمَا عَمِلُوٓاْۚ إِنَّ ٱللَّهَ عَلِيمُۢ بِذَاتِ ٱلصُّدُورِ
   And whosoever disbelieveth, let not his disbelief afflict thee (O Muhammad). Unto Us is their return, and We shall tell them what they did. Lo! Allah is Aware of what is in the breasts (of men).
   In context

   O Messenger! Whoever disbelieves in Allah, let not their disbelief grieve you. To Me alone they will return on the Day of Judgement; I will inform them of the evils they committed in the world and requite them for them. Indeed, Allah knows what is in the hearts; nothing is hidden from Him.

3. 35:39FatirCommand
   هُوَ ٱلَّذِي جَعَلَكُمۡ خَلَـٰٓئِفَ فِي ٱلۡأَرۡضِۚ فَمَن كَفَرَ فَعَلَيۡهِ كُفۡرُهُۥۖ وَلَا يَزِيدُ ٱلۡكَٰفِرِينَ كُفۡرُهُمۡ عِندَ رَبِّهِمۡ إِلَّا مَقۡتٗاۖ وَلَا يَزِيدُ ٱلۡكَٰفِرِينَ كُفۡرُهُمۡ إِلَّا خَسَارٗا
   He it is Who hath made you regents in the earth; so he who disbelieveth, his disbelief be on his own head. Their disbelief increaseth for the disbelievers, in their Lord's sight, naught save abhorrence. Their disbelief increaseth for the disbelievers naught save loss.
   In context

   It is He who made some of you, O people, succeed others on earth. Those who deny Allah and what the messengers brought, then the sin and retribution of their disbelief will be borne by them. Their disbelief does not harm their Lord. The disbelief of the disbelievers adds only to their Lord’s displeasure and hatred for them.