The Book of Bahir is one of the earliest works of Kabbalistic literature. The identity of the author and the time of its composition are unknown, but its earliest mentions are found among the Kabbalists of Provence in the early 13th century. Tradition attributes the book to the Tanna, Rabbi Nechunya ben HaKanah, who is also a central figure in the literature of Heichalot and Merkavah, and is mentioned at the beginning of the book. Aside from the opening sentence, which is attributed to Rabbi Nechunya ben HaKanah, the rest of the text is attributed to the Amoraim of Eretz Yisrael and unidentified sages (such as Rabbi Berechiah, Rabbi Nechemiah, Rabbi Avun, Rabbi Amora, and others).
According to the prevailing scholarly hypothesis today, its literary form took shape and was edited during the 12th century in Ashkenaz and Provence, although it is based on earlier sources that are difficult to locate and describe.
The Book of Bahir is a relatively short work, consisting of about two hundred sections, most of which are brief, written in Hebrew and Aramaic. The sections include a collection of midrashim in the style of the Midrashic literature of the Sages, some of which are attributed to the Tannaim and Amoraim.
The book begins with the statement: "Rabbi Nechunya ben HaKanah said: One verse says, 'And now they do not see the bright light, it is in the skies,'" and therefore it was called by the Kabbalists "Sefer HaBahir" (the Book of Brightness). From this sentence, the title "Midrash of Rabbi Nechunya ben HaKanah" was also derived, which was used by Nachmanides, one of the early commentators who mentions the book. However, among Kabbalists, "Bahir" became the accepted name for the book.