Differences of opinions that occur between the [Scholars] of the Ummah are from two angles;
Firstly: differences in the furoo’ (subsidiary issues), and in issues of ijtihaad (qualified striving to reach the truth); such that when a person – whether it is a judge, muftee, writer, or teacher – strives to arrive at a ruling and is correct, he is rewarded two-fold.
But if he strives and is mistaken, then he is rewarded once.
Secondly: Differences in matters of usool (fundamentals); such as the issues related to Allaah’s Attributes, al-Qadr (Predestination and Pre-Decree), Eemaan (faith), and their like.
These cause those who oppose [such usool] to be regarded as deviants, because of them opposing the proofs from the Book and the Sunnah, and that which the Salafus-Saalih (Pious Predecessors) – the Companions and those who followed them in goodness – were agreed upon.”
Ref: Tanbeehaatul-Lateefah (p.93).
Posted by Abdul Kareem Ibn Ozzie