Surah Al-Anfal 8:73

وَٱلَّذِينَ كَفَرُوا۟ بَعْضُهُمْ أَوْلِيَآءُ بَعْضٍ ۚ إِلَّا تَفْعَلُوهُ تَكُن فِتْنَةٌ فِى ٱلْأَرْضِ وَفَسَادٌ كَبِيرٌ

And those who disbelieved are allies of one another. If you do not do so [i.e., ally yourselves with other believers], there will be fitnah [i.e., disbelief and oppression] on earth and great corruption.

Translation: Saheeh International

Tafsir

And those who disbelieve are allies of one another in terms of mutual support and inheritance and so there is no inheriting between you and them. Unless you do this unless you ally yourselves with the believers and sever relations with the disbelievers there will be sedition in the land and great corruption with …

Excerpt from Tafsir al-Jalalayn, commentary on 8:73, via Quran.com. The reader has the full commentary and 9 more tafsirs.