Bihar al-anwar (Oceans of Lights) is a monumental encyclopedia of hadiths which attempts to collect all Shi'ite traditions in a single work and which classifies them by subject matter. It was compiled in the Safavid period by the famous theologian Muhammad Baqir Majlisi (d. 1110/1698-9 or 1111/1699-1700). The importance the work has possessed since its compilation as the standard reference work for all Shi'ite studies can hardly be overemphasized. One indication of its popularity is that, despite its enormous size, it was published twice in lithographed form in the nineteenth century. The modern edition of the work fills 110 volumes of approximately 400 pages each. 

Majlisi collected his traditions from numerous earlier sources. As examples, we can mention a few of the works from which he derived the hadiths in the present collection, works which have been independently published in modern times. Shaykh al-Saduq, the author of one of the four basic works on Shi'ite hadiths referred to above, compiled dozens of authoritative hadith collections, each of which usually follows a particular theme. His al-Tawhid collects traditions which illustrate the profession of God's Unit. His 'Uyun akhbar al-Rida gathers together everything that has been related about Imam 'Ali al-Rida, the eighth Imam, whose tomb in Mashhad is the holiest site of pilgrimage in Iran. The work contains such things as descriptions of the Imam's mother, explanations of the reason his name was chosen, all the sayings which have been recorded from him, and traditions concerning his death and the miracles which have occurred at his tomb. Shaykh al-Saduq's al-Khisal demonstrates the importance of numbers in the traditions. In twelve long chapters he records all the hadiths which mention the numbers one to twelve. The author of al-Ihtijaj, Abu Mansur Ahmad ibn 'al-Tabarsi (d. 599/1202-3), rejects the views of certain of his contemporaries who had claimed that the Prophet and the Imams never engaged in argumentation. He collects together traditions in which their discussions with opponents have been recorded.