Sefer Yahel Ohr, also known by the title Hadrat Kodesh, is a commentary on the Zohar by the Rabbi Elijah of Vilna, better known by the acronym Gra or [Vilna Gaon](https://www.sefaria.org/topics/vilna-gaon?tab=author-works-on-sefaria. The Gra’s explanations were arranged and annotated by Rabbi Samuel Luria. Luria included another Zohar commentary, Nefesh David, by Rabbi David Luria, as an appendix. Ohr is the Hebrew word for light, so the title describes the enlightenment that the Gra’s explanations provide to the student of the Zohar.