وَٱلَّذِينَ كَفَرُوا۟ بَعْضُهُمْ أَوْلِيَآءُ بَعْضٍ ۚ إِلَّا تَفْعَلُوهُ تَكُن فِتْنَةٌ فِى ٱلْأَرْضِ وَفَسَادٌ كَبِيرٌ
Commentary:
The pronoun "it" in تفعلوه (if you do it not) refers to what has been said in the previous verse, i.e. helping oppressed Muslims as well as fulfilling compacts with non-Muslims. The verse purports to say that if this teaching is not observed by Muslims, the result will be oppression and disturbance in the earth.
If this principle is not observed by Muslims, there will be oppression, tyranny and disturbance in the land.