Read Ruku 58 of the Quran

يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَكُونُوا۟ كَٱلَّذِينَ كَفَرُوا۟ وَقَالُوا۟ لِإِخْوَٰنِهِمْ إِذَا ضَرَبُوا۟ فِى ٱلْأَرْضِ أَوْ كَانُوا۟ غُزًّۭى لَّوْ كَانُوا۟ عِندَنَا مَا مَاتُوا۟ وَمَا قُتِلُوا۟ لِيَجْعَلَ ٱللَّهُ ذَٰلِكَ حَسْرَةًۭ فِى قُلُوبِهِمْ ۗ وَٱللَّهُ يُحْىِۦ وَيُمِيتُ ۗ وَٱللَّهُ بِمَا تَعْمَلُونَ بَصِيرٌۭ ﴿١٥٦﴾

O you who have believed, do not be like those who disbelieved and said about their brothers when they traveled through the land or went out to fight, "If they had been with us, they would not have died or have been killed," so Allah makes that [misconception] a regret within their hearts. And it is Allah who gives life and causes death, and Allah is Seeing of what you do.

وَلَئِن قُتِلْتُمْ فِى سَبِيلِ ٱللَّهِ أَوْ مُتُّمْ لَمَغْفِرَةٌۭ مِّنَ ٱللَّهِ وَرَحْمَةٌ خَيْرٌۭ مِّمَّا يَجْمَعُونَ ﴿١٥٧﴾

And if you are killed in the cause of Allah or die - then forgiveness from Allah and mercy are better than whatever they accumulate [in this world].

وَلَئِن مُّتُّمْ أَوْ قُتِلْتُمْ لَإِلَى ٱللَّهِ تُحْشَرُونَ ﴿١٥٨﴾

And whether you die or are killed, unto Allah you will be gathered.

فَبِمَا رَحْمَةٍۢ مِّنَ ٱللَّهِ لِنتَ لَهُمْ ۖ وَلَوْ كُنتَ فَظًّا غَلِيظَ ٱلْقَلْبِ لَٱنفَضُّوا۟ مِنْ حَوْلِكَ ۖ فَٱعْفُ عَنْهُمْ وَٱسْتَغْفِرْ لَهُمْ وَشَاوِرْهُمْ فِى ٱلْأَمْرِ ۖ فَإِذَا عَزَمْتَ فَتَوَكَّلْ عَلَى ٱللَّهِ ۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلْمُتَوَكِّلِينَ ﴿١٥٩﴾

So by mercy from Allah, [O Muhammad], you were lenient with them. And if you had been rude [in speech] and harsh in heart, they would have disbanded from about you. So pardon them and ask forgiveness for them and consult them in the matter. And when you have decided, then rely upon Allah. Indeed, Allah loves those who rely [upon Him].

إِن يَنصُرْكُمُ ٱللَّهُ فَلَا غَالِبَ لَكُمْ ۖ وَإِن يَخْذُلْكُمْ فَمَن ذَا ٱلَّذِى يَنصُرُكُم مِّنۢ بَعْدِهِۦ ۗ وَعَلَى ٱللَّهِ فَلْيَتَوَكَّلِ ٱلْمُؤْمِنُونَ ﴿١٦٠﴾

If Allah should aid you, no one can overcome you; but if He should forsake you, who is there that can aid you after Him? And upon Allah let the believers rely.

وَمَا كَانَ لِنَبِىٍّ أَن يَغُلَّ ۚ وَمَن يَغْلُلْ يَأْتِ بِمَا غَلَّ يَوْمَ ٱلْقِيَـٰمَةِ ۚ ثُمَّ تُوَفَّىٰ كُلُّ نَفْسٍۢ مَّا كَسَبَتْ وَهُمْ لَا يُظْلَمُونَ ﴿١٦١﴾

It is not [attributable] to any prophet that he would act unfaithfully [in regard to war booty]. And whoever betrays, [taking unlawfully], will come with what he took on the Day of Resurrection. Then will every soul be [fully] compensated for what it earned, and they will not be wronged.

أَفَمَنِ ٱتَّبَعَ رِضْوَٰنَ ٱللَّهِ كَمَنۢ بَآءَ بِسَخَطٍۢ مِّنَ ٱللَّهِ وَمَأْوَىٰهُ جَهَنَّمُ ۚ وَبِئْسَ ٱلْمَصِيرُ ﴿١٦٢﴾

So is one who pursues the pleasure of Allah like one who brings upon himself the anger of Allah and whose refuge is Hell? And wretched is the destination.

هُمْ دَرَجَـٰتٌ عِندَ ٱللَّهِ ۗ وَٱللَّهُ بَصِيرٌۢ بِمَا يَعْمَلُونَ ﴿١٦٣﴾

They are [varying] degrees in the sight of Allah, and Allah is Seeing of whatever they do.

لَقَدْ مَنَّ ٱللَّهُ عَلَى ٱلْمُؤْمِنِينَ إِذْ بَعَثَ فِيهِمْ رَسُولًۭا مِّنْ أَنفُسِهِمْ يَتْلُوا۟ عَلَيْهِمْ ءَايَـٰتِهِۦ وَيُزَكِّيهِمْ وَيُعَلِّمُهُمُ ٱلْكِتَـٰبَ وَٱلْحِكْمَةَ وَإِن كَانُوا۟ مِن قَبْلُ لَفِى ضَلَـٰلٍۢ مُّبِينٍ ﴿١٦٤﴾

Certainly did Allah confer [great] favor upon the believers when He sent among them a Messenger from themselves, reciting to them His verses and purifying them and teaching them the Book and wisdom, although they had been before in manifest error.

أَوَلَمَّآ أَصَـٰبَتْكُم مُّصِيبَةٌۭ قَدْ أَصَبْتُم مِّثْلَيْهَا قُلْتُمْ أَنَّىٰ هَـٰذَا ۖ قُلْ هُوَ مِنْ عِندِ أَنفُسِكُمْ ۗ إِنَّ ٱللَّهَ عَلَىٰ كُلِّ شَىْءٍۢ قَدِيرٌۭ ﴿١٦٥﴾

Why [is it that] when a [single] disaster struck you [on the day of Uhud], although you had struck [the enemy in the battle of Badr] with one twice as great, you said, "From where is this?" Say, "It is from yourselves." Indeed, Allah is over all things competent.

وَمَآ أَصَـٰبَكُمْ يَوْمَ ٱلْتَقَى ٱلْجَمْعَانِ فَبِإِذْنِ ٱللَّهِ وَلِيَعْلَمَ ٱلْمُؤْمِنِينَ ﴿١٦٦﴾

And what struck you on the day the two armies met was by permission of Allah that He might make evident the [true] believers.

وَلِيَعْلَمَ ٱلَّذِينَ نَافَقُوا۟ ۚ وَقِيلَ لَهُمْ تَعَالَوْا۟ قَـٰتِلُوا۟ فِى سَبِيلِ ٱللَّهِ أَوِ ٱدْفَعُوا۟ ۖ قَالُوا۟ لَوْ نَعْلَمُ قِتَالًۭا لَّٱتَّبَعْنَـٰكُمْ ۗ هُمْ لِلْكُفْرِ يَوْمَئِذٍ أَقْرَبُ مِنْهُمْ لِلْإِيمَـٰنِ ۚ يَقُولُونَ بِأَفْوَٰهِهِم مَّا لَيْسَ فِى قُلُوبِهِمْ ۗ وَٱللَّهُ أَعْلَمُ بِمَا يَكْتُمُونَ ﴿١٦٧﴾

And that He might make evident those who are hypocrites. For it was said to them, "Come, fight in the way of Allah or [at least] defend." They said, "If we had known [there would be] fighting, we would have followed you." They were nearer to disbelief that day than to faith, saying with their mouths what was not in their hearts. And Allah is most Knowing of what they conceal -

ٱلَّذِينَ قَالُوا۟ لِإِخْوَٰنِهِمْ وَقَعَدُوا۟ لَوْ أَطَاعُونَا مَا قُتِلُوا۟ ۗ قُلْ فَٱدْرَءُوا۟ عَنْ أَنفُسِكُمُ ٱلْمَوْتَ إِن كُنتُمْ صَـٰدِقِينَ ﴿١٦٨﴾

Those who said about their brothers while sitting [at home], "If they had obeyed us, they would not have been killed." Say, "Then prevent death from yourselves, if you should be truthful."

وَلَا تَحْسَبَنَّ ٱلَّذِينَ قُتِلُوا۟ فِى سَبِيلِ ٱللَّهِ أَمْوَٰتًۢا ۚ بَلْ أَحْيَآءٌ عِندَ رَبِّهِمْ يُرْزَقُونَ ﴿١٦٩﴾

And never think of those who have been killed in the cause of Allah as dead. Rather, they are alive with their Lord, receiving provision,

فَرِحِينَ بِمَآ ءَاتَىٰهُمُ ٱللَّهُ مِن فَضْلِهِۦ وَيَسْتَبْشِرُونَ بِٱلَّذِينَ لَمْ يَلْحَقُوا۟ بِهِم مِّنْ خَلْفِهِمْ أَلَّا خَوْفٌ عَلَيْهِمْ وَلَا هُمْ يَحْزَنُونَ ﴿١٧٠﴾

Rejoicing in what Allah has bestowed upon them of His bounty, and they receive good tidings about those [to be martyred] after them who have not yet joined them - that there will be no fear concerning them, nor will they grieve.

۞ يَسْتَبْشِرُونَ بِنِعْمَةٍۢ مِّنَ ٱللَّهِ وَفَضْلٍۢ وَأَنَّ ٱللَّهَ لَا يُضِيعُ أَجْرَ ٱلْمُؤْمِنِينَ ﴿١٧١﴾

They receive good tidings of favor from Allah and bounty and [of the fact] that Allah does not allow the reward of believers to be lost -