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

“[Remember the time] when you fled, paying no heed to anyone, while at your rear the Apostle was calling out to you - wherefore He requited you with woe in return for [the Apostle's] woe, so that you should not grieve [merely] over what had escaped you, nor over what had befallen you: for God is aware of all that you do.”

Then Allah mentioned how they turned their back on the Prophet (pbuh) because of their fear of the enemy, saying: (When ye climbed) the hill after being defeated (and paid no heed to anyone) paid no heed to the Prophet and did not wait for him, (while the messenger) Muhammad, (in your rear, was calling you (to fight)) he was behind you, O group of believers, saying: I am Allah's Messenger, stop and fight! (Therefore He rewarded you grief for (his) grief) in addition to the grief wrought upon you by Khalid Ibn al-Walid, He also inflicted on you the grief of death and defeat, (that (He might teach) you not to sorrow either for that which ye missed) of booty (or for that which befell you) and that you do not sorrow for that which befell you of deaths and injuries. (Allah is Informed of what ye do) in jihad as well as in defeat.