Sefer Yetzirah
Besides this halakhic work, Judah wrote a detailed commentary on the "Sefer Yetzirah." Like most commentaries on "Sefer Yetzirah", that by Judah helps little to an understanding of the text; on the contrary, it contains Judah's own rather diffuse, half-mystical, half-philosophical theological discussions. The author betrays an astonishing familiarity with the Talmudic-Midrashic literature, and gives extracts from works of the Geonim which are otherwise unknown.