The Arabs did not have the knowledge of heavenly and divine scriptures. Hence, when Nabi (sallallahu alaihi wa sallam) informed them of his nubuwwat, they sent a delegation to the Jews enquiring whether the rasuls (messengers) that had come before, were men or angels. The Jews replied that they were men. So their minds were clear that all rasuls were men like us. And they had to be men and not angels, for if they were angels, then angels do not get tired etc. So how will they be able to understand human life?
There are basically two categories of people: (1) ahluz zikr – those who have knowledge (2) ghair ahluz zikr (those who do not have knowledge). This is the system in worldly knowledge as well.
Then there are two types of texts that appear in the Qur’aan and Hadeeth: (1) Clear and categorical. Someone who has got the knowledge of this can follow this directly. For example, the prohibition of zina or the command of salaah etc. (2) Unclear and ambiguous or there seems to be a contradiction with other aayaat or ahaadeeth. To understand these, one’s knowledge needs to be extremely sound. When we are faced with such a text then the requisite is that we follow an imaam of fiqh. When people like Imaam Ghazaali, Imaam Raazi and even greater than them, Imaam Tirmizi (rahimahumullah) saw the need of following an imaam, then how much more in need are we. This is the consensus of all Ulama of the past that one will need to follow an imaam. In fact, the following of an imaam is a relief.