Read Ruku 170 of the Quran

يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ ٱتَّقُوا۟ ٱللَّهَ وَكُونُوا۟ مَعَ ٱلصَّـٰدِقِينَ ﴿١١٩﴾

O you who have believed, fear Allah and be with those who are true.

مَا كَانَ لِأَهْلِ ٱلْمَدِينَةِ وَمَنْ حَوْلَهُم مِّنَ ٱلْأَعْرَابِ أَن يَتَخَلَّفُوا۟ عَن رَّسُولِ ٱللَّهِ وَلَا يَرْغَبُوا۟ بِأَنفُسِهِمْ عَن نَّفْسِهِۦ ۚ ذَٰلِكَ بِأَنَّهُمْ لَا يُصِيبُهُمْ ظَمَأٌۭ وَلَا نَصَبٌۭ وَلَا مَخْمَصَةٌۭ فِى سَبِيلِ ٱللَّهِ وَلَا يَطَـُٔونَ مَوْطِئًۭا يَغِيظُ ٱلْكُفَّارَ وَلَا يَنَالُونَ مِنْ عَدُوٍّۢ نَّيْلًا إِلَّا كُتِبَ لَهُم بِهِۦ عَمَلٌۭ صَـٰلِحٌ ۚ إِنَّ ٱللَّهَ لَا يُضِيعُ أَجْرَ ٱلْمُحْسِنِينَ ﴿١٢٠﴾

It was not [proper] for the people of Madinah and those surrounding them of the bedouins that they remain behind after [the departure of] the Messenger of Allah or that they prefer themselves over his self. That is because they are not afflicted by thirst or fatigue or hunger in the cause of Allah, nor do they tread on any ground that enrages the disbelievers, nor do they inflict upon an enemy any infliction but that is registered for them as a righteous deed. Indeed, Allah does not allow to be lost the reward of the doers of good.

وَلَا يُنفِقُونَ نَفَقَةًۭ صَغِيرَةًۭ وَلَا كَبِيرَةًۭ وَلَا يَقْطَعُونَ وَادِيًا إِلَّا كُتِبَ لَهُمْ لِيَجْزِيَهُمُ ٱللَّهُ أَحْسَنَ مَا كَانُوا۟ يَعْمَلُونَ ﴿١٢١﴾

Nor do they spend an expenditure, small or large, or cross a valley but that it is registered for them that Allah may reward them for the best of what they were doing.

۞ وَمَا كَانَ ٱلْمُؤْمِنُونَ لِيَنفِرُوا۟ كَآفَّةًۭ ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍۢ مِّنْهُمْ طَآئِفَةٌۭ لِّيَتَفَقَّهُوا۟ فِى ٱلدِّينِ وَلِيُنذِرُوا۟ قَوْمَهُمْ إِذَا رَجَعُوٓا۟ إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ ﴿١٢٢﴾

And it is not for the believers to go forth [to battle] all at once. For there should separate from every division of them a group [remaining] to obtain understanding in the religion and warn their people when they return to them that they might be cautious.