Is separation permissible in Islam?

Division in religion is of two types: The first is blameworthy, and that is what constitutes a disagreement in doctrines and rulings established by consensus; whoever opposes them is following [their own] whims. The second is not blameworthy, and that is disagreement in jurisprudential branches and conjectural issues; the one who exerts effort (performs ijtihad) in them is rewarded. The disagreement among the Companions and Imams was of this type. However, the fanaticism of later generations to the opinion of a specific Imam and abandoning the truth led to enmity and hatred.