Read Ruku 57 of the Quran

يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِن تُطِيعُوا۟ ٱلَّذِينَ كَفَرُوا۟ يَرُدُّوكُمْ عَلَىٰٓ أَعْقَـٰبِكُمْ فَتَنقَلِبُوا۟ خَـٰسِرِينَ ﴿149﴾

O you who have believed, if you obey those who disbelieve, they will turn you back on your heels, and you will [then] become losers.

بَلِ ٱللَّهُ مَوْلَىٰكُمْ ۖ وَهُوَ خَيْرُ ٱلنَّـٰصِرِينَ ﴿150﴾

But Allah is your protector, and He is the best of helpers.

سَنُلْقِى فِى قُلُوبِ ٱلَّذِينَ كَفَرُوا۟ ٱلرُّعْبَ بِمَآ أَشْرَكُوا۟ بِٱللَّهِ مَا لَمْ يُنَزِّلْ بِهِۦ سُلْطَـٰنًۭا ۖ وَمَأْوَىٰهُمُ ٱلنَّارُ ۚ وَبِئْسَ مَثْوَى ٱلظَّـٰلِمِينَ ﴿151﴾

We will cast terror into the hearts of those who disbelieve for what they have associated with Allah of which He had not sent down [any] authority. And their refuge will be the Fire, and wretched is the residence of the wrongdoers.

وَلَقَدْ صَدَقَكُمُ ٱللَّهُ وَعْدَهُۥٓ إِذْ تَحُسُّونَهُم بِإِذْنِهِۦ ۖ حَتَّىٰٓ إِذَا فَشِلْتُمْ وَتَنَـٰزَعْتُمْ فِى ٱلْأَمْرِ وَعَصَيْتُم مِّنۢ بَعْدِ مَآ أَرَىٰكُم مَّا تُحِبُّونَ ۚ مِنكُم مَّن يُرِيدُ ٱلدُّنْيَا وَمِنكُم مَّن يُرِيدُ ٱلْـَٔاخِرَةَ ۚ ثُمَّ صَرَفَكُمْ عَنْهُمْ لِيَبْتَلِيَكُمْ ۖ وَلَقَدْ عَفَا عَنكُمْ ۗ وَٱللَّهُ ذُو فَضْلٍ عَلَى ٱلْمُؤْمِنِينَ ﴿152﴾

And Allah had certainly fulfilled His promise to you when you were killing the enemy by His permission until [the time] when you lost courage and fell to disputing about the order [given by the Prophet] and disobeyed after He had shown you that which you love. Among you are some who desire this world, and among you are some who desire the Hereafter. Then he turned you back from them [defeated] that He might test you. And He has already forgiven you, and Allah is the possessor of bounty for the believers.

۞ إِذْ تُصْعِدُونَ وَلَا تَلْوُۥنَ عَلَىٰٓ أَحَدٍۢ وَٱلرَّسُولُ يَدْعُوكُمْ فِىٓ أُخْرَىٰكُمْ فَأَثَـٰبَكُمْ غَمًّۢا بِغَمٍّۢ لِّكَيْلَا تَحْزَنُوا۟ عَلَىٰ مَا فَاتَكُمْ وَلَا مَآ أَصَـٰبَكُمْ ۗ وَٱللَّهُ خَبِيرٌۢ بِمَا تَعْمَلُونَ ﴿153﴾

[Remember] when you [fled and] climbed [the mountain] without looking aside at anyone while the Messenger was calling you from behind. So Allah repaid you with distress upon distress so you would not grieve for that which had escaped you [of victory and spoils of war] or [for] that which had befallen you [of injury and death]. And Allah is [fully] Acquainted with what you do.

ثُمَّ أَنزَلَ عَلَيْكُم مِّنۢ بَعْدِ ٱلْغَمِّ أَمَنَةًۭ نُّعَاسًۭا يَغْشَىٰ طَآئِفَةًۭ مِّنكُمْ ۖ وَطَآئِفَةٌۭ قَدْ أَهَمَّتْهُمْ أَنفُسُهُمْ يَظُنُّونَ بِٱللَّهِ غَيْرَ ٱلْحَقِّ ظَنَّ ٱلْجَـٰهِلِيَّةِ ۖ يَقُولُونَ هَل لَّنَا مِنَ ٱلْأَمْرِ مِن شَىْءٍۢ ۗ قُلْ إِنَّ ٱلْأَمْرَ كُلَّهُۥ لِلَّهِ ۗ يُخْفُونَ فِىٓ أَنفُسِهِم مَّا لَا يُبْدُونَ لَكَ ۖ يَقُولُونَ لَوْ كَانَ لَنَا مِنَ ٱلْأَمْرِ شَىْءٌۭ مَّا قُتِلْنَا هَـٰهُنَا ۗ قُل لَّوْ كُنتُمْ فِى بُيُوتِكُمْ لَبَرَزَ ٱلَّذِينَ كُتِبَ عَلَيْهِمُ ٱلْقَتْلُ إِلَىٰ مَضَاجِعِهِمْ ۖ وَلِيَبْتَلِىَ ٱللَّهُ مَا فِى صُدُورِكُمْ وَلِيُمَحِّصَ مَا فِى قُلُوبِكُمْ ۗ وَٱللَّهُ عَلِيمٌۢ بِذَاتِ ٱلصُّدُورِ ﴿154﴾

Then after distress, He sent down upon you security [in the form of] drowsiness, overcoming a faction of you, while another faction worried about themselves, thinking of Allah other than the truth - the thought of ignorance, saying, "Is there anything for us [to have done] in this matter?" Say, "Indeed, the matter belongs completely to Allah." They conceal within themselves what they will not reveal to you. They say, "If there was anything we could have done in the matter, some of us would not have been killed right here." Say, "Even if you had been inside your houses, those decreed to be killed would have come out to their death beds." [It was] so that Allah might test what is in your breasts and purify what is in your hearts. And Allah is Knowing of that within the breasts.

إِنَّ ٱلَّذِينَ تَوَلَّوْا۟ مِنكُمْ يَوْمَ ٱلْتَقَى ٱلْجَمْعَانِ إِنَّمَا ٱسْتَزَلَّهُمُ ٱلشَّيْطَـٰنُ بِبَعْضِ مَا كَسَبُوا۟ ۖ وَلَقَدْ عَفَا ٱللَّهُ عَنْهُمْ ۗ إِنَّ ٱللَّهَ غَفُورٌ حَلِيمٌۭ ﴿155﴾

Indeed, those of you who turned back on the day the two armies met, it was Satan who caused them to slip because of some [blame] they had earned. But Allah has already forgiven them. Indeed, Allah is Forgiving and Forbearing.