[Remember, O believers], when Allah promised you one of the two groups (8:7)

﴿وَإِذْ يَعِدُكُمُ اللَّهُ إِحْدَى الطَّائِفَتَيْنِ أَنَّهَا لَكُمْ وَتَوَدُّونَ أَنَّ غَيْرَ ذَاتِ الشَّوْكَةِ تَكُونُ لَكُمْ وَيُرِيدُ اللَّهُ أَن يُحِقَّ الْحَقَّ بِكَلِمَاتِهِ وَيَقْطَعَ دَابِرَ الْكَافِرِينَ﴾
[ الأنفال: 7]

8:7 [Remember, O believers], when Allah promised you one of the two groups - that it would be yours - and you wished that the unarmed one would be yours. But Allah intended to establish the truth by His words and to eliminate the disbelievers

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.

And (remember) when Allah promised you (Muslims) one of the two parties (of the enemy i.e. either the army or the caravan) that it should be yours, you wished that the one not armed (the caravan) should be yours, but Allah willed to justify the truth by His Words and to cut off the roots of the disbelievers (i.e. in the battle of Badr).

phonetic Transliteration

Waith yaAAidukumu Allahu ihda alttaifatayni annaha lakum watawaddoona anna ghayra thati alshshawkati takoonu lakum wayureedu Allahu an yuhiqqa alhaqqa bikalimatihi wayaqtaAAa dabira alkafireena

Abdullah Yusuf Ali - Translation

Behold! Allah promised you one of the two (enemy) parties, that it should be yours: Ye wished that the one unarmed should be yours, but Allah willed to justify the Truth according to His words and to cut off the roots of the Unbelievers;-

Safi-ur-Rahman al-Mubarakpuri

And (remember) when Allah promised you (Muslims) one of the two parties, that it should be yours; you wished that the one not armed should be yours, but Allah willed to justify the truth by His Words and to cut off the roots of the disbelievers.

Page 177 English transliteration