(Taken from Kitab al Irshad By Sheikh al Mufid)
Al-Baqir Muhammad b. Ali b. al-Husayn, peace be on them, was out of (all) his brothers the successor of his father, Ali b. al-Husayn, his testamentary trustee (wasi), and the one who undertook (qaim) the office of Imam after him. He surpassed all of them through his outstanding merit (fadl) in traditional knowledge (ilm), asceticism and leadership. He was the most renowned of them, the one among them who was most esteemed by both non-Shia (amma) and Shia (khassa), and the most able of them. None of the sons of al- Hasan and al-Husayn, peace be on them, showed the same ability in knowledge of religion, traditions, the sunna, the knowledge of the Qur'an and the life of the Prophet (sira), and the techniques of literature, as Abu- Jafar (Muhammad al-Baqir) showed. The surviving Companions (of the Prophet), the leading members of the next generation (tabieun) and the leaders of the Muslim jurists reported the principal features (ma'alim) of religion on his authority. By virtue of his outstanding merit he became a signpost (of knowledge) to his family. Proverbs were coined about him and reports and verses were written to describe him.
He, peace be on him, was born in Medina, in 57 A.H. (676/7). He died in 114 A.H. (732) at the age of fifty-seven. He was a (leading) member of the Hashimite family within the Hashimites. He was a (leading) descendant of Ali among the descendants of Ali. He was buried in (the cemetery of) al-Baqi'i in (Medina) the city of the Apostle, may God bless him and his family.
In the testamentary bequest (wasiyya) which the Commander of the faithful, peace be on him, made to his children, mention was made of Muhammad b. Ali b. al-Husayn and of his trusteeship. The Apostle of God, may God bless him and his family, named him and caused him to be known as the one who split open (religious) knowledge (ulum) as the narrators of tradition (ashab al-athar) report.
The Shia give an account of the tablet which Gabriel, peace be on him, brought down to the Apostle of God, may God bless him and his family, from heaven. (The Apostle) gave it to Fatima, peace be on her. In it are the names of the Imams after (the Apostle) and in it is Muhammad b. Ali, the Imam after his father.
The Shia also report that God, the Mighty and High, sent down to His Prophet, the blessings and peace of God be on him, a document sealed with twelve seals. He ordered him to give it to the Commander of the faithful, peace be on him, and to tell him to break the first seal, and he should act according to what is in (that part of the document). At the time of his death, he should pass it to his son, al-Hasan, peace be on him, and tell him to break the second seal and act according to what is in (that part of) the document. At the time of his death he should pass it to his brother al-Husayn, peace be on him. He should tell him to break the third seal and act according to what is below it. Then at his death, he should pass it to his son, Ali b. al-Husayn al- Akbar (the elder) and he should instruct him in a similar way. Then Muhammad should pass it to his son right down to the last of the Imams.
They report also numerous designations (nusus) of him for the Imamate after his father on the authority of the Prophet, may God bless him and his family, on the authority of the Commander of the faithful and on the authority of al-Hasan, al-Husayn and Ali b. al- Husayn, peace be on them.
The people report (accounts) of his outstanding virtues and accomplishments which would be too numerous to include. We will mention what will be sufficient in meaning for our purposes, if God wills.
Abu Jafar, peace be on him, recounted reports of the beginnings of history (mubtada') and reports of the prophets. Stories of the campaigns of the Prophet (maghazi) were written on his authority. (Men) followed the practices of the Prophet (sunan) on his authority and relied on him with regard to the rites of the pilgrimage which he reported on the authority of the Apostle of God, may God bless him and his family. They (also) wrote a commentary of the Qur'an on his authority. Both the Shia (khassa) and the non-Shia (amma) report traditions on his authority. He debated with the exponents of individual reasoning (ahl al-ara') and the people learnt a great deal of theology (ilm al-kalam) from him.
He, peace be on him, used to say: "The people cause us great trouble. We summon them but they do not answer us. If we abandoned them, they would be guided by no one."
He, peace be on him, (also) used to say: "What is it that the people hate in us who are the family of the House of Mercy, the Tree of Prophethood, the Source of Wisdom, (the people) frequented by angels and (those upon whom) inspiration descended?"
He, peace be on him, died and left behind seven sons. Each of his brothers had great merit, even though they did not attain his merit because of his position with regard to the Imamate, because of his rank with God with regard to closeness and love (wilaya), and because of his position with regard to succession (khilafa) of the Prophet, may God bless him and his family. The period of his Imamate and of his undertaking the position of his father in the succession (on behalf of) God, the Mighty and High, over His servants was nineteen years.