(We shall cast terror into the hearts of those who disbelieve) [3:151]. Said al-Suddi: “After Uhud, Abu Sufyan and the idolaters headed toward Mecca. But after they traversed a certain distance, they felt regret, saying: ‘Evil is that which we have done! We massacred them such that none of them remained except those who fled from the battlefield and then we left them alone. Go back and exterminate them’. But when they decided to do so, Allah, exalted is He, cast terror in their hearts which made them decide against what they had resolved to do. Allah, exalted is He, then revealed this verse”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou