Sheikh al-Saduq, also known as Abu Ja'far Muhammad ibn Ali al-Saduq, was a prominent Islamic scholar and theologian in the 10th century. He is best known for his contributions to Shia Islam, particularly in the fields of hadith (traditions of the Prophet Muhammad) and theology. His works helped to preserve and transmit important religious texts and teachings. He authored several significant books, including Man La Yahduruhu al-Faqih, which is one of the four major hadith collections in Shia Islam. Sheikh al-Saduq's scholarship played a crucial role in shaping Shia thought and practice, making him a respected figure in Islamic history.