Muhammad ibn Ali al-Baqir (peace be upon him)

Muhammad was born in Medina around 676. In 680, as a young child, he witnessed the Battle of Karbala, where his grandfather Husayn ibn Ali (peace be upon him) and most of his relatives were massacred by the forces of the Umayyad Caliph Yazid ibn Muawiyah (r. 680–683). After his father's martyrdom around 712, Muhammad (peace be upon him) was recognized by most of his father's followers as the next Imam.

Muhammad al-Baqir lived a pious and scholarly life in Medina, attracting a growing number of followers, students, and visitors. During his nearly twenty-year imamate, he is considered to have laid the doctrinal and religious foundations of Twelver Shiism. He can also be considered the father of Ismaili and Zaydi jurisprudence. He ultimately contributed significantly to the Twelver interpretation of the Quran. Most of Imam Baqir's disciples were based in Kufa, in present-day Iraq, many of whom later became prominent Shia jurists and traditionists. Some of these, such as Zurarah ibn Ayan, may have occasionally disagreed with Al-Baqir, who would not have approved such independent views if they had gone beyond the general theological and legal framework presented by the (Shiite) Imams. In Sunni Islam, Imam Baqir is regarded as an authority on Sharia and the Prophetic tradition.

According to most Shia accounts, Imam Muhammad Baqir died around 732 and was poisoned by the Umayyads. He is buried in the Baqi' cemetery in Medina, but the shrine over his grave has been destroyed twice by Wahhabis. Imam Baqir was succeeded by his eldest son, Ja'far al-Sadiq, who further developed Shia theology and law.