Those present who reported what happened at the scene...
Those present who reported what happened at the scene, either did not pay attention to this or that peculiarity, or, if they did recognise it, did not mention this or that particular aspect. Because of inaccurate description of the circumstances, traditions may appear to contradict each other, but in reality they each apply to different circumstances. This inaccuracy caused difficulties in recognising the exact meaning of an instruction given to us by the Prophet.
Accordingly, the companions who had the honour of close companionship with the Prophet supported "ijtihad". That is they realised the necessity for a thorough investigation of the text of the hadith and the situation in which it occurred. The different aspects of the hadith were probed, since the apparent meaning of the tradition is often different from the real aim of the codifier.
It has been pointed out earlier, that these difference were largely due to faulty copying or shortcomings on the part of the reporters.
Those companions of the Holy Prophet (s.a.w.) who were just and trustworthy and who were also reporters of traditions sometimes reproduced the statement of the Prophet (s.a.w.) in exactly the same words in which they had heard it, while sometimes, in place of the text of the tradition, they would state the order or commandment which was inferred from the tradition in question.
In the first instance their position is that of a reporter or traditionalist, and in the second they have the position of learned scholars who declare their opinion about the meaning of the hadiths; the latter are also called "mujtihids". All Muslims who do not have this ability and so therefore follow the opinion of the mujtahid, are called "muqallid". The act of acting on the verdicts of a mujtahid is called "taqlid".
After a thorough examination of this matter we find that during the time of the Holy Prophet (s.a.w.), the door of ijtihad was open and the companions of the Prophet (s.a.w.) themselves acted upon it; of course at that time ijtihad was not so strong as it is today, because the people could ask the Prophet (s.a.w.) directly about any matter they were not sure of.
As time passed, however, and relations between the Arabs and non-Arabs increased, there were difficulties in understanding the correct meanings of the Arabic language. The number of traditions and reports became larger. Among them were very many doubtful and fabricated traditions.