Ali 'Imran 3:153

Ith tusAAidoona walatalwoona AAala ahadin warrasooluyadAAookum fee okhrakum faathabakum ghammanbighammin likay la tahzanoo AAala mafatakum wala ma asabakum wallahukhabeerun bima taAAmaloon

[Remember] when you [fled and] climbed [the mountain] without looking aside at anyone while the Messenger was calling you from behind. So Allāh 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 Allāh is [fully] Aware of what you do.

When you were going away, not even turning to look at anyone, and the Messenger was calling you from behind you. He awarded you sorrow for sorrow, so that you should not grieve (in future) over what you lost, or for what you suffered. Allah is All-Aware of what you do.