Idra Raba and Idra Zuta: Two compilations from the Zohar, the first in the portion of Naso and the second in the portion of Ha'azinu. The term "Idra" in Greek means a gathering or assembly of scholars, and these Idrot (plural of Idra) are gatherings of the students of Rabbi Shimon bar Yochai who were studying the esoteric secrets of the Torah from a sage. When their assembly was large and abundant with students, it was called "Idra Raba Kadisha" (the Holy Great Assembly). Idra Zuta, which is a continuation of Idra Raba, was written on the day Rabbi Shimon bar Yochai passed away. Before his passing, he revealed deep secrets to them. Rabbi Elazar, his son, would explain them, and Rabbi Abba, the scribe, would write them down in the book. See "Idra" in the Otzar Yisrael encyclopedia. Pious individuals and mystics enjoyed studying the Idrot on the nights of Shavuot (the Festival of Weeks) and Hoshana Rabbah. In Jerusalem, it was customary to study them on the tomb of the prophet Samuel on the day of his passing, the 28th of Iyar. In Safed, they recite them on the night of Lag BaOmer, which is the anniversary of Rabbi Shimon bar Yochai's passing. They were printed in special booklets, such as "Idra Rabta and Zutarta etc.", "Idra of the portion Mishpatim and Sifra DeTzni'uta" (Kushta 1748); "Holy Idrot and letters of Rabbi Nathan Spira etc." (Amsterdam 1808); "Order of the Holy Idrot etc." (Venice 1711), and more.