How are the first three centuries described as righteous when some deviant groups emerged during them, such as the followers of Abdullah ibn Saba, the Khawarij, and those who killed Husayn? And why do we take our understanding of the religion from the followers of the Tabi'in (successors of the companions), even though we were not explicitly commanded to follow them, despite the fact that the group that must be followed is only the Companions and the Tabi'in?

The emergence of heretical sects in the late era of the Companions and the Tabi'un does not negate the goodness of those generations, because "goodness" does not mean their complete absence of evils. The argument for following the followers of the Tabi'un is the same as the argument for following the Tabi'un themselves, which is based on the texts that describe them as good, meaning that they are more knowledgeable, more pious, and closer to the truth. The best generations are the first three, as stated in multiple authentic hadiths, and some narrations may also include the fourth.