وَٱلَّذِينَ كَفَرُوا۟ بَعْضُهُمْ أَوْلِيَآءُ بَعْضٍ ۚ إِلَّا تَفْعَلُوهُ تَكُن فِتْنَةٌۭ فِى ٱلْأَرْضِ وَفَسَادٌۭ كَبِيرٌۭ
“As for the disbelievers, they are guardians of one another. And unless you [believers] act likewise (i.e., unless you ally with the other believers), there will be great oppression and corruption in the land.”
Surah al-Anfal was revealed on the plains of Badr regarding the battle and its aftermath.