Talking about the vastness of the Ahl al-Bayt’s (as) knowledge, Imam al-Sadiq (as), once, said to Abu Basir,
“O! Abu Muhammad! Almighty Allah did not grant anything to the Prophets (as) before He had decided it for Prophet Muhammad (S). He thus granted Prophet Muhammad (S) everything He had given the Prophets (as), and we are the inheritors of Muhammad (S), and we have with us the tablets of Abraham (as) and Moses (as).”
Abu Basir asked, “Do you mean these tablets?” “Yes, I do”, answered the Imam. (Ref: See Diya al-Alamin, vol. 2 – manuscript).
Bakr ibn Bakr al-Sayrafi has reported that he heard Abu Abdullah (al-Sadiq (as)) saying,
“We have things that make us dispense with Opinionism (ray), analogy (qiyas), and all people, while all people do need us. This is a book, dictated by the Prophet (S) and handwritten by Imam Ali (as), which comprises every legal and illegal item. Due to this book too, we know whether you will accept or deny the advice that we offer to you when you ask us anything.(Ref: See Diya al-Alamin, vol. 2 – manuscript).
Imam al-Sadiq (as) has developed the knowledge with his creative thoughts and precise sights filling the earth with his sciences. He once said:
“Ask me before losing me. No one will speak to you as I do.”
No other one said this statement except his grandfather, Imam Ali (as). Informing about his knowledge, he said,
“I swear by Allah (SwT) that I know the Book of Allah (SwT) from the beginning to the end as it is part of my existence. It contains the knowledge of the heavens and the news of earth. It includes what happened formerly and what will happen in the future. Allah the Almighty and Majestic, said, ‘The manifestation of everything can be found inside it (i.e. the Holy Quran).’”
Another thing that demonstrated his high knowledge was the four thousands students who distributed sciences and cultures in all Islamic countries and spread the features of religion and the religious instructions.
THE LIFE OF IMAM JA’FAR AL SADIQ (AS) – BAQAR SHARIF AL QARASHI