ثُمَّ أَنزَلَ عَلَيْكُم مِّن بَعْدِ الْغَمِّ أَمَنَةً نُّعَاسًا يَغْشَى طَائِفَةً مِّنكُمْ وَطَائِفَةٌ قَدْ أَهَمَّتْهُمْ أَنفُسُهُمْ يَظُنُّونَ بِاللَّهِ غَيْرَ الْحَقِّ ظَنَّ الْجَاهِلِيَّةِ يَقُولُونَ هَل لَّنَا مِنَ الْأَمْرِ مِن شَيْءٍ قُلْ إِنَّ الْأَمْرَ كُلَّهُ لِلَّهِ يُخْفُونَ فِي أَنفُسِهِم مَّا لَا يُبْدُونَ لَكَ يَقُولُونَ لَوْ كَانَ لَنَا مِنَ الْأَمْرِ شَيْءٌ مَّا قُتِلْنَا هَاهُنَا قُل لَّوْ كُنتُمْ فِي بُيُوتِكُمْ لَبَرَزَ الَّذِينَ كُتِبَ عَلَيْهِمُ الْقَتْلُ إِلَى مَضَاجِعِهِمْ وَلِيَبْتَلِيَ اللَّهُ مَا فِي صُدُورِكُمْ وَلِيُمَحِّصَ مَا فِي قُلُوبِكُمْ وَاللَّهُ عَلِيمٌ بِذَاتِ الصُّدُورِ
Then He sent down to you safety after grief—a drowsiness that came over a group of you—while another group, anxious only about themselves, entertained false notions about Allah, notions of [pagan] ignorance. They say, ‘Do we have any role in the matter?’ Say, ‘Indeed the matter belongs totally to Allah.’ They hide in their hearts what they do not disclose to you. They say, ‘Had we any role in the matter, we would not have been slain here.’ Say, ‘Even if you had remained in your houses, those destined to be slain would have set out toward the places where they were laid to rest, so that Allah may test what is in your breasts, and that He may purge what is in your hearts, and Allah knows well what is in the breasts.’
Agha Ali Puya Commentary
Commentary on Quran 3:154
[Pooya/Ali Commentary 3:154] Those who had fought hard to create panic in the enemy's camp had an agreeable and refreshing sleep, because their faith in Allah and His prophet was certain and they knew what would ultimately happen. It was a divine blessing the true faithfuls enjoyed on that day as a recompense for their selfless and devotional service in the cause of Allah. There was another group which questioned and doubted the Holy Prophet's promise of divine interposition. They harboured inwardly disapproval and unbelief, and spoke into their (like-minded) comrades' ears about the sure defeat against a formidable enemy; and also grumbled regarding their advice to remain in Madina instead of coming to Uhad where their friends and relatives had been killed. Disbelief in Allah and His prophet, in the end, incited them to abandon the Holy Prophet in the time of trouble. Even if they stayed at home, those of them, who were destined to die, would have gone to their place of death. Allah has made known that which was in their hearts (hypocrisy) to the people who will come in this world till the day of resurrection.