Answer
Husayn ibn Ali, the grandson of the Prophet Muhammad, was the grandfather of Muhammad al-Baqir. Al-Baqir was an influential Shia Imam and scholar who played a significant role in developing Shia theology and jurisprudence. His grandfather, Husayn, was a revered figure in Shia Islam, known for his martyrdom at the Battle of Karbala in 680 CE.