Abu Ja`far Muammad bin Jarir at-Tabari in the introduction to his history book said:
Let him who examines this book of mine know that I have relied, as regards everything I mention therein which I stipulate to be described by me, solely upon what has been transmitted to me by way of reports which I cite therein and traditions which I ascribe to their narrators, to the exclusion of what may be apprehended by rational argument or deduced by the human mind, except in very few cases. This is because knowledge of the reports of men of the past and of contemporaneous views of men of the present do not reach the one who has not witnessed them nor lived in their times except through the accounts of reporters and the transmission of transmitters, to the exclusion of rational deduction and mental inference. Hence, if I mention in this book a report about some men of the past, which the reader of listener finds objectionable or worthy of censure because he can see no aspect of truth nor any factual substance therein, let him know that this is not to be attributed to us but to those who transmitted it to us and we have merely passed this on as it has been passed on to us.
“Tareeh at-Tabari” 1997, volume 1, Darul kutub al-Ilmiyah, p 13.