Shaikh Mufeed (ra) went to two erudite scholars, Ibne Abd Allah and Ibne Abi Jafar, who were impressed with his knowledge that they sometimes felt that they themselves were unable to reply to the queries of the young student.
It is narrated that once Ibne Jafar expressed his inability to reply to his queries and asked Sheik Mufeed to rather meet Ali ibne Eesa and seek his guidance. Ali ibne Eesa Rumani was the authority on Ilm e Kalam in Baghdad those days. One day Sheik Mufeed agreed to go and meet Ali Rumani but told to his mentor that he didn’t know where the scholar ran his classes. The teacher sent some of his students, who were residents of Baghdad, to guide Sheik Mufeed to the place of Ali Ibne Eesa. Those days Sheik Mufeed was known only as Mohammed ibne Mohammed ibne Noman and he wasn’t known with the appellation of Sheik Mufeed. Mohammed’s guides took him along to the place where Ali ibne Eesa was conducting his class. Mohammed saw that there were a large number of students attending to the teaching of the mentor. Therefore he got some place to sit at the entrance of the room where the footwear was kept.
As the class progressed some students checked out and some new arrivals would join. Therefore Mohammed slowly advanced towards the place from where Ali ibne Eesa was giving his talk. At that time he saw the slave of Ali ibne Eesa came and informed that a person from Basra was waiting outside to be admitted.. His master asked him if the person looked like a scholar. The slave wasn’t able to make a guess. His master asked the slave to call the person to his presence.
When the visitor came, in deference to the guest from outside, Ali ibne Eesa stood up to receive him and asked the visitor to sit close to him. They discussed various topics when suddenly the visitor asked a question about Hadit e Ghaar (the tradition of the Cave) and Hadith e Ghadeer (the tradition of Ghadeer).
Hadeet e Ghadeer is the tradition when the Prophet (s.a) declared to a large gathering of Muslims—‘Mun kunto maula fa haada Ali Maula’—‘Ali is the master of those of whom I am the master’.
The Hadeet e Ghaar is about the cave in which the Prophet (s.a) was stranded along with one of his companions.
Ali ibne Eesa replied that Hadit e Ghaar was a Dirayat and Hadeet e Ghadeer was a Riwayat and a Riwayat cannot be given ascendancy over a Dirayat.
Dirayat and Riwayat are the two most intricate aspects of Ilm e Hadit. I shall briefly explain about them. Riwayat in common parlance is merely hearsay while Dirayat is supported by positive proof or evidence of the happening. Therefore Ali ibne Eesa said that Hadeet e Ghaar has ascendancy over Hadeet e Ghadeer. The man from Basra kept quiet over this.
But Sheik Mufeed couldn’t control himself. Although raw in age, he took courage in his hands and asked the master if he had permission to ask a question. Ali ibne Eesa looked at the youth in surprise and gave him permission to ask the question.
He asked if someone fought a battle against the Imam e Adil (the Just and legitimate Ruler) what would be his ruling. Ali ibne Eesa replied that such a person would be termed a Kaafir (an infidel}. He thought for a while and said that the person may not be termed an infidel but he will be termed a Faasiq (a transgressor) and Faajir (a Sinner).
Now Sheik Mufeed asked Ali ibne Eesa his opinion about Ali (a.s). He replied that Ali (a.s) was Imam e Adil and the Muslims had pledged their allegiance to him.
Sheik Mufeed now asked Ali ibne Eesa his opinion about those who arraigned themselves against him in the battle field. Ali ibne Eesa replied that those persons were repentant of their act and they are pardoned.
Now Sheik Mufeed told Ali ibne Eesa, “You say that those persons were repentant. Now according to your definition their coming to the battlefield against Ali (a.s) would be termed a Dirayat and their expression of repentance would at best be a Riwayat. You yourself have said earlier that Dirayat has preference over Riwayat!”
Ali ibne Eesa was nonplussed for sometime. Then he asked Sheik Mufeed, “Tell me who is your mentor?” He replied, “I am a student of Ali ibne Abd Allah and Ibne Abi Jafar.” Ali ibne Eesa went inside his house and returned after a short while and gave to Sheik Mufeed a letter addressed to his mentors. He went back to his mentor and gave the letter to him. The teacher opened the letter, read it, smiled and asked his young charge, “Tell me what transpired at the place of Ali ibne Eesa?” He said, “Why are you asking this question?” He said, “Ali ibne Eesa, who is the leading scholar of Baghdad has highly praised you in the letter and said that you are certainly ‘Mufeed’ (useful) for Deen e Islam! He has given to you the appellation of Mufeed. Tell me now what has transpired there?” Sheik Mufeed narrated to his mentor the entire event. The mentor now affirmed that his young ward was truly Mufeed!
Shi‘ite Authorities in the Age of Major Occultation Part 1: Sheikh Mufid