Miṭpaḥat Sefarim
Miṭpaḥat Sefarim is a book  which deals with the composition of the Book of Zohar and its contents written by Rabbi Jacob Emden (Ya'avetz. In Hebrew: יעב"ץ). His purpose was is to challenge the attribution of the book to Tanna from the 2nd century AD by Rabbi Shimon Bar Yochai, and to attribute it to a later author. It was intended to combat the Sabbath movement, which relied on passages in the Book of Zohar to confirm the proclamation of the Kabbalist Shabtai Zvi about himself as the Messiah in the middle of the 17th century.