Those who have hitherto examined Islam's methodical report-card maintain that the age of the reign of Harun and that of Mamun have been known as a brilliant scholarly epoch in the literary history of Islam.
In the course of this eminent period of time the Muslims succeeded in becoming acquainted with the western scientific findings through translating the Greek work, and thereafter they profoundly studied those versions and added large numbers of new scholarly subjects of research such as studies on theoretical and rational sciences to those themes.
The Muslim scientists attained success to discover many acids like nitrus acid, sulphuric acid and other substances as the infernal stone.
The access to the western philosophy as well as the availability of the Greek written sources and the acquaintance with the views and doctrines of Aristotle, Socrates, Plato and their disciples, paved the way for the Muslim scholars to develop their studies on natural sciences and on metaphysical issues as well.
The freedom of thought provided and permitted by Islam made facilities for the scholars of other religions to hold debate sessions on exchanging their ideas in connection with questions and problems concerning the precepts and doctrines of their creeds.
Likewise, the expansion of the Islamic territories caused the association of the Muslims with non-Muslim peoples including the Jews, the Christians and even too many atheists.
These opponents tried to propound disputes and invent doubtful allegories about the faith of the Muslims.
The situation was very critical and the ideological assault seemed to be more dangerous than a military invasion in those days.
Mamun,the Abbasid caliph was a very clever, shrewd and cunning politician. In order to get closer to Imam Reza (A.S.), he would arrange inter-faith scholarly debates, and would usually invite the Holy Imam(A.S.) to participate in these meetings. There he would pose the most complicated religious and scientific questions to the scholars.
On Tuesdays, Mamun used to invite scholars of different religious persuasions to Marw. After meals he would perform ablution, perfume himself and enter the gathering. The debate hall was furnished with the most expensive carpets, and the debate would continue until evening.
Imam Reza (A.S.), however, knew the objectives behind all this and would always warn his close followers not to be deceived by Mamun's actions. He would say: "By Allah! None other than he will kill me. There is no other option, we should be patient till this ends."
Mamun's real purpose in inviting the intelligentsia and top scholars from different lands to debate with the Holy Imam(A.S.), was his vain desire to see one of the scholars overcome Imam Reza(A.S.)-the true heir and real successor of the Holy Prophet of Islam(S.A.W.). In this way Mamun wanted to degrade the exalted position attached to the person of the Holy Imam(A.S.) among the scholars.
Learned scholars of the Jews Christians, Zoroastrians, idol and star-worshippers and the atheists, as well as the different sects of Islam, would debate with Imam Reza (A.S.) and finally leave the gatherings in admiration for the God-given knowledge of the Holy Prophet of Islam's(S.A.W.) rightful successor. The Holy Imam(A.S.) used to answer them from their own books and on the basis of their own reasoning by presenting logical explanations in their own language.
All this had a great impact upon the revival and spread of the Islamic teachings.Imam Reza(A.S.), thus successfully safeguarded and propagated the ideals,teachings and principles of Islam.In this way the Holy Imam (A.S.), also protected the rights of the Muslims and awakened them.
After every debate, Imam Reza's(A.S.) popularity would soar, and respect and esteem for him would grow higher among the scholars, to the extent that people used to regard the Holy Imam(A.S.) more worthy of the caliphate. The spies of Mamun would keep him informed about the general public opinion regarding the proceedings of the debates, making the caliph more jealous and more spiteful of the Holy Imam(A.S.).
But for the time being Mamun maintained his outward behaviour of respect and on his request Imam Reza (A.S.) compiled two books: "Fiqh ur-Reza(A.S.)" and "Tibb ur-Reza(A.S.)", which respectively deal with the principles of Islamic jurisprudence and prescriptions of health and hygiene.