Jaʿfar ibn Muhammad al-Sādiq (Arabic: جعفر بن محمد الصادق‎) was a descendant of Muhammad and a prominent Muslim jurist. He is revered as an Imam by the adherents of Shi’a Islam and as a renowned Islamic scholar and personality by Sunni Muslims. The Shi’a Muslims consider him to be the sixth Imam or leader and spiritual successor to Muhammad. The internal dispute over who was to succeed Ja’far as Imam led to schism within Shi’a Islam. Al-Sadiq was celebrated among his brothers and peers and stood out among them for his great personal merits.He is highly respected by both Sunni and Shi’a Muslims for his great Islamic scholarship, pious character, and academic contributions.

Although he is perhaps most famous as the founder of Shi’a Islamic fiqh, known as Ja’fari jurisprudence, he had many other accomplishments. He was the teacher of many subsequent Muslim scholars such as the founders of both Sunni and Shi’a Islamic schools of jurisprudence. As well as being considered an Imam of the Shi’a, he is revered by the Naqshbandi Sunni Sufi chain. He was a polymath: an astronomer, alchemist, Imam, Islamic scholar, Islamic theologian, writer, philosopher, physician, physicist and scientist [In later years in the west this would have been called a natural philosopher]. He was also the teacher of the famous chemist, Jābir ibn Hayyān, and a contemporary of Abū Ḥanīfa,the founder of the Hanafi school of Sunni Islamic jurisprudence.

Someone once asked Ja’far Al-Sadiq to show him God. Ja’far Al-Sadiq replied, “Look at the sun.” The man replied that he could not look at the sun because it was too bright.

Ja’far Al-Sadiq replied: “If you cannot see the created, how can you expect to see the creator?”

More information on Wikipedia here.