9:81
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.
Context in Surah At-Tawbah
Nearby ayahs help place verse 9:81 in sequence and meaning.
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.
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.
فَلْيَضْحَكُوا۟ قَلِيلًا وَلْيَبْكُوا۟ كَثِيرًا جَزَآءًۢ بِمَا كَانُوا۟ يَكْسِبُونَ
So let them laugh a little and [then] weep much as recompense for what they used to earn.
فَإِن رَّجَعَكَ ٱللَّهُ إِلَىٰ طَآئِفَةٍ مِّنْهُمْ فَٱسْتَـْٔذَنُوكَ لِلْخُرُوجِ فَقُل لَّن تَخْرُجُوا۟ مَعِىَ أَبَدًا وَلَن تُقَـٰتِلُوا۟ مَعِىَ عَدُوًّا ۖ إِنَّكُمْ رَضِيتُم بِٱلْقُعُودِ أَوَّلَ مَرَّةٍ فَٱقْعُدُوا۟ مَعَ ٱلْخَـٰلِفِينَ
If Allah should return you to a faction of them [after the expedition] and then they ask your permission to go out [to battle], say, "You will not go out with me, ever, and you will never fight with me an enemy. Indeed, you were satisfied with sitting [at home] the first time, so sit [now] with those who stay behind."