Consequences of disunity and weakness

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.