Answer
Ali al-Sajjad was the father of Muhammad al-Baqir. Muhammad al-Baqir was the fifth Shia Imam, and a prominent Islamic scholar and theologian. He is known for his vast knowledge and wisdom, and is considered one of the most important figures in Shia Islam. Muhammad al-Baqir's father, Ali al-Sajjad, was the fourth Shia Imam, and is also known for his piety and scholarship.