The Repentance
ٱلَّذِينَ يَلْمِزُونَ ٱلْمُطَّوِّعِينَ مِنَ ٱلْمُؤْمِنِينَ فِى ٱلصَّدَقَـٰتِ وَٱلَّذِينَ لَا يَجِدُونَ إِلَّا جُهْدَهُمْ فَيَسْخَرُونَ مِنْهُمْ ۙ سَخِرَ ٱللَّهُ مِنْهُمْ وَلَهُمْ عَذَابٌ أَلِيمٌ
Those who criticize the contributors among the believers concerning [their] charities and [criticize] the ones who find nothing [to spend] except their effort, so they ridicule them - Allah will ridicule them, and they will have a painful punishment.
Nearby ayahs help place verse 9:79 in sequence and meaning.
فَأَعْقَبَهُمْ نِفَاقًا فِى قُلُوبِهِمْ إِلَىٰ يَوْمِ يَلْقَوْنَهُۥ بِمَآ أَخْلَفُوا۟ ٱللَّهَ مَا وَعَدُوهُ وَبِمَا كَانُوا۟ يَكْذِبُونَ
So He penalized them with hypocrisy in their hearts until the Day they will meet Him - because they failed Allah in what they promised Him and because they [habitually] used to lie.
أَلَمْ يَعْلَمُوٓا۟ أَنَّ ٱللَّهَ يَعْلَمُ سِرَّهُمْ وَنَجْوَىٰهُمْ وَأَنَّ ٱللَّهَ عَلَّـٰمُ ٱلْغُيُوبِ
Did they not know that Allah knows their secrets and their private conversations and that Allah is the Knower of the unseen?
ٱسْتَغْفِرْ لَهُمْ أَوْ لَا تَسْتَغْفِرْ لَهُمْ إِن تَسْتَغْفِرْ لَهُمْ سَبْعِينَ مَرَّةً فَلَن يَغْفِرَ ٱللَّهُ لَهُمْ ۚ ذَٰلِكَ بِأَنَّهُمْ كَفَرُوا۟ بِٱللَّهِ وَرَسُولِهِۦ ۗ وَٱللَّهُ لَا يَهْدِى ٱلْقَوْمَ ٱلْفَـٰسِقِينَ
Ask forgiveness for them, [O Muhammad], or do not ask forgiveness for them. If you should ask forgiveness for them seventy times - never will Allah forgive them. That is because they disbelieved in Allah and His Messenger, and Allah does not guide the defiantly disobedient people.
فَرِحَ ٱلْمُخَلَّفُونَ بِمَقْعَدِهِمْ خِلَـٰفَ رَسُولِ ٱللَّهِ وَكَرِهُوٓا۟ أَن يُجَـٰهِدُوا۟ بِأَمْوَٰلِهِمْ وَأَنفُسِهِمْ فِى سَبِيلِ ٱللَّهِ وَقَالُوا۟ لَا تَنفِرُوا۟ فِى ٱلْحَرِّ ۗ قُلْ نَارُ جَهَنَّمَ أَشَدُّ حَرًّا ۚ لَّوْ كَانُوا۟ يَفْقَهُونَ
Those who remained behind rejoiced in their staying [at home] after [the departure of] the Messenger of Allah and disliked to strive with their wealth and their lives in the cause of Allah and said, "Do not go forth in the heat." Say, "The fire of Hell is more intensive in heat" - if they would but understand.