That is because they opposed Allah and His Messenger. And whoever opposes (8:13)

Almuntakhab Fi Tafsir Alquran Alkarim

This train of events succeeding one another were occasioned on account of their hostility to Allah and to His Messenger; and he who is hostile to Allah and His Messenger shall realize that Allah punishes severely indeed

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(8:13) This is because they defied Allah and His Messenger. Whoever defies Allah and His Messenger must know that Allah is severe in punishment. *11

That is because they opposed Allah and His Messenger. And whoever opposes meaning

*11). In recounting the events of the Battle of Badr, the Qur'an aims to explain the significance of the word al-anfal (spoils of war). In the opening verse of the surah the Muslims were told that they should not deem the spoils to be a reward for their toil. Rather, the spoils should constitute a special reward granted to the Muslims by God, to Whom the spoils rightfully belong. The events recounted here support this. The Muslims could reflect on the course of events and see for themselves to what extent the victory they had achieved was due to God's favour, and to what extent it was due to their own efforts.
 

That is because they opposed Allah and His Messenger. And whoever opposes meaning in Urdu

یہ اس لیے کہ ان لوگوں نے اللہ اور اس کے رسولؐ کا مقابلہ کیا اور جو اللہ اور اس کے رسولؐ کا مقابلہ کرے اللہ اس کے لیے نہایت سخت گیر ہے