Introduction
In the Islamic world, some figures have emerged who have always been celebrated by Muslims for their special qualities. Imam ‘Alī bin Mūsā al-Riḍā (P.B.U.H.) is among these iconic figures who has invariably been respected and praised by all Muslims whether Shiite or Sunnite for his noble lineage, rich knowledge, spirituality, and morality.
The views and expressions of Shiites and Sunnites about his holiness can be classified in six sections:

A: Lineage
‘Alī bin Mūsā al-Riḍā (P.B.U.H.) is the son of Mūsā bin Ja'far. His mother's name was Taktam who after the birth of Imam Riḍā (P.B.U.H.) was named as Tāhira. What is significant in this regard is that all Islamic denominations are unanimous on the fact that Riḍā (P.B.U.H.) is the son of Holy Prophet Muhammad (P.B.U.H. & H.F.). This fact is being testified by Hākim Neyshābūrī who says, "One of the greatest honors and virtues of ‘Alī bin Mūsā al-Riḍā (P.B.U.H.) is that he is a descendant of the Holy Prophet (P.B.U.H. & H.F.)."; he insists that it is believed by Sunnites as well. 
There are also narrations that refer to the lineage of Imam Riḍā (P.B.U.H.). Some of these narrations belong to Shiite narrative resources and assert that Imam Riḍā (P.B.U.H.) is the Messenger of Allah's descendant and his beloved one. Such narrations can also be seen in Sunnite resources, some of which have traced the lineage of his holiness back to the Holy Prophet (P.B.U.H. & H.F.). Concerning his children, there can also be observed some reports both in Shiite and Sunnite narrations. Two points have been stipulated in Shiite narrations; the first point is that Sabīka bore Imam Riḍā (P.B.U.H.) a son named Muhammad Taqī and the second point is that his holiness had no children from Ma'mūn's daughter, Ummi Habība. But more children than one have been mentioned for his holiness in Sunnite narrations. 

B: Scientific and Religious Status
Another issue that has been considered about Imam Riḍā (P.B.U.H.) by both Shiites and Sunnite Muslims is his scientific and religious status. According to Shiites, the Immaculate Imams (P.B.U.T.) are the heir to prophets and the most significant heritage of prophets is their knowledge. Hence, Imam Riḍā's father (P.B.U.H.) bestowed him the title "the Scholar of the Prophet's Household [Ālim Āl Muhammad]". 
In various narrations quoted by Shiite and Sunnite Muslims, several references have been made to his holiness's knowledge regarding the Qur'an, ideological and theological issues, revealed religions and books, and jurisprudence and medicine. In this regard, Imam Riḍā (P.B.U.H.) himself states, "I sat in the Prophet's shrine and whenever Medina's scholars faced a problem that they were helpless in solving it, they came to me and received the answer" . Concerning the Imam's knowledge and his proficiency in the Qur'an, Ibrāhīm bin ‘Abbās said, "I have never seen somebody more knowledgeable than him. Ma'mūn frequently asked him about various issues and the Imam answered them while all his answers were examples taken from the Qur'an". 
Imam Riḍā's knowledge of hidden truths and his acquaintance with various languages are other signs of his holiness' broad knowledge that have been indicated in Shiite narrations. Meanwhile, the Imam's debates have a special significance as they show his majesty's knowledge and wisdom regarding different theological issues. The books and literature ascribed to him by the Shiites are regarded as the sign of the Imam's scientific genius. In ‘Uyūn Akhbār al-Riḍā, Sheikh Sadūq attributed a thesis to his holiness; the Imam wrote it in reply to Muhammad bin Sanān's request for information on legal rulings' reasons. Sahīfat al-Riḍā and Risāla al-Dhahabīyya are among the renowned books ascribed to Imam Riḍā (P.B.U.H.) which have been written on hygienical issues and medical prescriptions at the request of Ma'mūn. 
Education is another part of his holiness' scientific life. It is said that his holiness has instructed a number of students during the eighteen years of his Imamate in Medina and two years in Marw some of whom are considered as great Shiite Hadith transmitters and scientists. Hadith scholars have estimated their numbers up to 318. 
Regarding the scientific status of the Imam, many narrations have also been quoted by Sunnite scholars and authorities. As quoted in a tradition, while Imam Riḍā (P.B.U.H.) was no more than 20 years old, he sat in the Prophet's mosque and answered people's questions. 
Having confirmed this narration, Hākim Neyshābūrī says, "Although Imam Riḍā (P.B.U.H.) was a little more than 20 years old, his holiness did issue judicial decrees and Sunnite authorities quoted many narrations from him. When the Imam lost his children, Bilāzirī addressed him in the following words, "Your are greater than our description and we are not able to offer any piece of advice to you. You have enough knowledge and may Allah offer condolences on you." Muhammad bin Jarīr Tabarī said about his holiness, "Ma'mūn appointed ‘Alī bin Mūsā al-Riḍā (P.B.U.H.) as his vice-regent; for he could not find anyone more pious and wiser than him among the descendants of Abbās and ‘Alī (P.B.U.H.)." 
Other great figures like Ibn Abī al-Hadīd , Dhahabī, Shāfe'ī , and Ibn 'Arabī are among those people who have celebrated Imam Riḍā (P.B.U.H.) and indicated some points on the scientific status of his holiness.
It is worth mentioning that the admiration and consideration of Imam's scientific status is not restricted to the past scholars of Sunnism but many Sunnite contemporary men of ideas have expressed their minds in this regard. The author of Imam Riḍā (P.B.U.H.) in the Sunni Narrations has innovatively quoted the statements or words of the Sunnite authorities/scholars regarding his holiness respectively from the early Islamic centuries until the contemporary era. For example, regarding Imam Riḍā (P.B.U.H.), Yusuf bin Ismāeīl Nabhānī Shāfi'ī, one of the scholars of 14th century, has said, "He is one of the great Imams, the bright torches, and a member of the Holy Prophet's Household (P.B.U.H. & H.F.); he is the originating source of knowledge, mysticism, nobility, chivalry, and magnanimity." 
Moreover, regarding the scientific standing of the Imam, ‘Alī bin Muhammad 'Abdallāh Fikarī mentioned, "Ibrāhīm bin ‘Abbās has said, 'There was no case that he [the Imam] was asked about something and the Imam had not given a convincing answer in response'". The Sunnite traditionists have quoted narrations in which Imam Riḍā (P.B.U.H.) predicated some future events such as Barmecides' fall/decline , the burial sites of Hārūn and himself , murder of Amīn by Ma'mūn , and the like.

C: The Spiritual Status and Manners of Imam Riḍā (P.B.U.H.) 
Following codes of ethics and subscribing to moral values are of the outstanding characteristics of the infallible Household of the Prophet (P.B.U.T.). This characteristic has a particular prominence in Imam Riḍā's life; because he is the successor of the Messenger of Allāh (P.B.U.H. & H.F.); since the Holy Prophet (P.B.U.H. & H.F.) is the best role model for Muslims, his successor should be like him as well. Many narrations have been quoted in the Shiite and Sunnite literature in this regard. Due to their multiplicity, we only mention some of these narrations from the Sunnite resources. 
Referring to the spiritual manners of Imam Riḍā (P.B.U.H.), Ibrāhīm bin ‘Abbās said, "‘Alī bin Mūsā al-Riḍā (P.B.U.H.) had little sleep and kept fast very often, ..., He did many good deeds. He gave his alms at night so as to cover his identity by dark. He sat on a mat in the summer and on a sheepskin in the winter". In this regard, Ibn Jawzī wrote, "‘Alī bin Mūsā Riḍā (P.B.U.H.), whose lineage came from Banī Hāshim is offered the title of "Riḍā" and was very truthful". 
Ibn Talha said, "‘Alī bin Mūsā is the most magnanimous, noble, and perfect child of Mūsa bin Ja'far". In another narration, he said about his holiness, "His prophetic character and temperament indicates his noble descent that he has inherited from his fathers." 
Ibn Abī al-Hadīd has also described the Imam as the wisest, the most generous, and the most good-natured of all people. About the Imam, Mawsilī Shāfi'ī said, "His holiness had a great patience and insight and was endlessly patient. He excelled in piety, fear of Allah, courage, and magnanimity". 
Qalqashandī Shāfi'ī, one of the scholars of the 9th century, said, "When Ma'mūn saw Imam Riḍā's bright knowledge, ... piety, and his sincere austerity to the [material] world, he appointed him to the vice-regency". 
The spiritual and moral qualities of his holiness were so conspicuous that they were even manifested in the non-Shiite poetry such as the poems attributed to Hasan bin Hānī known as Abū Nuwās. Mīr Shāfi'ī, one of the Sunnite poets of the tenth century, composed the following poem for the Imam: 
"Salutations to thee, the Household of Tāhā and Yāsīn ,
Salutations to thee, the Household of the best of prophets;
Salutations to the garden that holds in itself, 
the Imam that the religion and world are proud of him". 

D: Narrations Quoted from Imam Riḍā (P.B.U.H.)
Among the noteworthy things here are the narrations quoted from his holiness by the Shiite and Sunnite. Part of these narrations are those that have been quoted by Imam Riḍā (P.B.U.H.) without referring to others. And the other part includes those narrations which his holiness has quoted from his fathers and the Holy Prophet (P.B.U.H. & H.F.). The second set of narrations are known as "Silsilat al-Dhahab", namely the Golden Chain traditions, because all links in the chain of their narrators were all infallible and among the prominent Muslims of the time. The renowned tradition of "Silsilat al-Dhahab" which his holiness stated in Neyshābūr is regarded in this part.
When the Imam wanted to leave Neyshābūr, some traditionists and scholars asked him to recite a tradition. Imam Riḍā (P.B.U.H.) who was sitting in a litter on a mount, took his head out and narrated from his forefathers, "My father, Mūsa bin Ja'far, from his father, and Muhammad bin ‘Alī from his father, and ‘Alī bin Husain from his father, and Amīr al-Mu‘menīn from the Messenger of Allah and he from the revelation angel, and Gabriel quoted from the Almighty Allah, "Lā Ilāha ila Allāh (There is no god save Allah) is My firm fortress. Whosoever enters this bastion will be safe from My wrath." The narrator continued, "After his mount took a few steps, the Imam called us and said, 'This has conditions, and I am among its conditions.'" In addition to the narrations of the Shiite traditionists, such as Sheikh Sadūq, Arbalī, and Allāma Majlisī , this tradition is also quoted by the Sunnite narrators. It is noteworthy that there are two traditions known as the Golden Chain tradition in the Sunnite books which are similar in chains but different in denotation; one of them is the famous Fortress tradition [Hadīth Hiṣn] and the other one is the Faith tradition . Making a comprehensive research on these two traditions and their narrators , the author of the book Imam Riḍā (P.B.U.H.) in the Sunni Traditions said, "In the Sunnite resources, this tradition has been narrated by about fifty transmitters since the 3rd century up to now" . Of course, as the Shiite resources differ in transmitting this tradition, there are differences in the Sunnite resources as well. 
As an example, the Fortress tradition has been quoted in two ways. In most narrations like those of Khwāja Pārsā Hanafī and Qāzī Bahjat Afandī Shāfe'ī, this tradition ends with the sentence "He will not suffer My wrath" . But in some other narrations like that of Qundūzī, it ended with the sentence "It depends on some conditions, and I am considered to be one of those conditions" . 
The same story goes regarding the Faith tradition . At the request of some scholars of Neyshābūr, his holiness said, "True faith implies oral acknowledgement, heart-felt knowledge and action according to principles". Like the Fortress tradition [Hadīth Hiṣn], there are different narrations for this tradition, but they were considered as authentic by most Sunnites. 
Besides these renowned traditions, there are numerous narrations from Imam Riḍā (P.B.U.H.) in the Sunnite resources, which reveal the significant position of his holiness among Muslims and the positive approach of the Sunnite toward the Prophet's Household (P.B.U.H. & H.F.).

E. Imam Riḍā's Miracles
Another issue that has been addressed by both the Shiites and Sunnites is ‘Alī bin Mūsā al-Riḍā's miraculous deeds. In the Shiite and Sunnite narrative resources, innumerable miracles have been ascribed to his holiness; the indication of a number of them goes beyond the limits of this short paper. Thus, we only mention a few number of them as examples. Imam Riḍā's prayer for rain is one of the oft-quoted miracles by both the Shi'ite and Sunnite. As narrated by Hākim Neyshābūrī, after the Imam's arrival in Marw, the rumor quickly swept the town that for his holiness' presence the rain has stopped. Being both happy and upset on hearing the rumor, Ma'mūn requested the Imam to say prayers for rain. In response to people and Ma'mūn's request, Imam Riḍā (P.B.U.H.) headed towards the desert on Monday and after saying two raka't prayers and praising Allah, raised his hands and prayed, "O' Allah! You granted us, Ahl al-Bayt, great rights and these people invocated to us as you ordered; they are waiting for Your blessing. So, quench them with a useful, heavy, and harmless rain". 
The narrator said, "After ‘Alī bin Mūsā al-Riḍā's prayers, rain clouds appeared in the sky and thunderstorms began. Thinking it was rainy, people sought to find shelters. Meanwhile the Imam said, 'These clouds are not for this region'. This happened several times until once his holiness said, "These are the clouds Allah sent to you. So, be grateful, thank your Creator for this blessing and mercy, and go to your homes. Because if you do not go to your homes, these clouds will not rain for you.' And it happened so." 
Apart from this miracle, so many other events have been quoted on Imam Riḍā's miraculous deeds and a number of books have been published in this regard. 

F: Pilgrimage to Imam Riḍā (P.B.U.H.)
Another issue which is of high significance and has been always noted by both the Shiites and Sunnites and there are a great number of narrations and accounts on it is the pilgrimage to his holiness and its virtues. In the Shiite and Sunnite narrative resources, there have been quoted so many narrations from the Holy Prophet (P.B.U.H. & H.F.) and the other infallibles (P.B.U.T.).
Narrating from the Prophet (P.B.U.H. & H.F.), Imam Sādiq (P.B.U.H.) stated, "A part of my body will be buried in Khurāsān; each believer who makes a pilgrimage to him, Allah will settle him in the Heaven and will guard him from the Hell fire". 
Nu'mān bin Sa'd narrated from Imam ‘Alī (P.B.U.H.), "A man of my descendants, whose name is the same as mine and his father's name is Ibn Umrān Mūsā, will be buried in Khurāsān. Whosoever makes a pilgrimage to him in his loneliness, Allah will forgive all his past and future sins even if they were as many as the stars on the sky, rain drops, and tree leaves". 
Ibrāhīm bin Ishāq Nahāwandī narrated from Imam Riḍā (P.B.U.H.), "Whosoever makes a pilgrimage to me from a far distance, I will help him in three places to save him from the difficulties of those circumstances; when his book of deeds is given to his hand, at the time of crossing Sirāt Bridge, and at the time of counting deeds". 
Hākim Neyshābūrī on the authenticity of Imam Riḍā (P.B.U.H.) who quoted from the Prophet (P.B.U.H. & H.F.), "A part of my body will be buried in Khurāsān; everybody who is involved in a difficulty or is culpable if s/he makes a pilgrimage to him, the Almighty Allah will obviate his difficulty and forgive his sins". 
'Āyisha narrated from the Honorable Prophet (P.B.U.H. & H.F.), " 'Whosoever makes a pilgrimage to my son in Ṭūs, it is as if s/he has made a Hajj pilgrimage'. 'Āyisha asked the Prophet, 'One Hajj?!' The Prophet said in reply, 'Two Hajj pilgrimages.' 'Āyisha asked, 'Two Hajj?!' The Messenger of Allah said, 'Three Hajj.' 'Āyisha kept silent and told no more words". 
Juwainī Shāfe'ī narrated, "Someone came to Imam Riḍā (P.B.U.H.) and told him, 'O' the son of the Messenger of Allah! I saw the Prophet (P.B.U.H. & H.F.) in my dream. He asked me, 'How will you feel if a part of my body is buried in your land? How will you keep my trust?' Then, he asked the Imam, 'What did the Prophet (P.B.U.H. & H.F.) mean?' Imam Riḍā (P.B.U.H.) said in reply, 'I am the one who will be buried in your land. I am the part of the Prophet's body. And I am the very gracious person that if someone makes a pilgrimage to me knowing my true right, my forefathers and I will intercede him. Whosoever will be interceded by us will be saved'". 
Due to such narrations, Sunnite scholars have invariably paid attention to the pilgrimage to the Holy Shrine of his holiness. The author of Imam Riḍā (P.B.U.H.) in the Sunni Traditions mentioned in detail various pilgrimages of the Sunnite authorities and scholars to the Holy Shrine of Imam Riḍā (P.B.U.H.). 

Conclusion
Imam Riḍā (P.B.U.H.) is among the few figures who have been invariably praised by both the Shiites and Sunnites. One of the most important factors involved in this fact is his unique status among the Imams (P.B.U.T.) and his own manners in different circumstances. Considering the fact that there are few people like the Imam who have been popular and respected among various Muslim denominations, we can benefit from Imam Riḍā's character and manners as a significant factor for the unity and convergence of Muslims' views.