[Remember, O believers], when Allāh promised you one of the two groups1 - that it would be yours - and you wished that the unarmed one would be yours. But Allāh intended to establish the truth by His words and to eliminate the disbelievers
Translation: Saheeh International (English)
1 i.e., either the caravan of Quraysh or their army.
Allah reminds the believers who were arguing about when Allah promised them success over one of the groups of the idolaters: either the caravan with its sizeable wealth, so that they could take its bounty, or a group of fighters whom they would encounter and achieve victory over them; but they had wanted it to be the caravan, as this would be easy to take without having to fight. Yet Allah willed for the truth to be established through commanding them to fight, to kill the leaders of the idolaters, and to capture many of them so that the strength of Islam would become clear.