Qur'an 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.”

Al-Anfaal 8:73 · Saheeh International