Sefer Yeẓirah (The book of formation) is a Jewish cosmogonic book which focuses on the role of the decimal number system (sefirot) and the twenty-two letters of the Hebrew alphabet in the creation and in the created world. Considered a canonical Jewish text since the tenth century—notably, the same period in which the book is first attested—Sefer Yeẓirah became one of the most influential compositions for Jewish mysticism and Kabbalah. Unique in style and content, it has attracted remarkable attention both in Jewish and non-Jewish circles, fascinating scholars from various disciplines as well as a broader readership. Despite the rich scholarship devoted to it, Sefer Yeẓirah has not been fully deciphered yet, especially for what concerns its authorship, dating, and ultimate significance.

With his masterful monograph, Tzahi Weiss offers a clever new interpretation and contextualization of Sefer Yeẓirah, which, for the first time, takes into account and interrelates the actual subject of the book, its textual tradition, and its reception history. The identification of the precise interest of Sefer Yeẓirah in the speculation on the twenty-two Hebrew letters and their creative powers enables Weiss to draw solid comparisons with Syriac Christian literature, and, ultimately, to trace the intellectual matrix from which the book developed. Weiss shows how the nuances of the linguistic, physiologic, astrological, and cosmological notions displayed in the text point to a sophisticated late antique Jewish tradition that cannot be identified with rabbinic Judaism. Challenging the main theories on the time and context of Sefer Yeẓirah, he convincingly demonstrates that the book was “written and edited around the seventh century by Jews who were familiar with Syriac Christianity” (2). Showing how the history of the text is interwoven with its reception, Weiss argues for the existence of a mystical-mythical-magical interpretation of Sefer Yeẓirah prior to the twelfth century. The idea that late antique and early medieval Judaism was much more nuanced than the monolithic and rabbinocentric portrait outlined by a certain type of scholarship is the fil rouge of the book. Weiss situates both the formation and the earliest reception of Sefer Yeẓirah in a nonrabbinic milieu, showing that the text not only crystallized in an intellectual world neatly detached from both rabbinic culture and the known magico-mystical circles spinning in the rabbinic orbit—those that produced the hekhalot literature—but also, already in an early age, was transmitted and interpreted by Jews clearly interested in mysticism and magic and not only by “a limited section of the rabbinical elite” (104).

The volume consists of an introduction, five chapters, a short epilogue, and three appendices. The introduction discusses the main issues which complicate a definitive contextualization of Sefer Yeẓirah, explaining how Weiss's theory interconnects with or challenges the most relevant studies on the topic. This section should be read together with appendix 1, which unveils the anachronism of the argument for an Abbasid context for Sefer Yeẓirah.

In the first three chapters, Weiss advances his thesis on the composition of Sefer Yeẓirah, starting by demonstrating that—albeit contested by church authorities—letter speculation developed remarkably also in Syriac Christian marginal circles, the specific intellectual environment in which Sefer Yeẓirah was conceived (chapter 1). In his analysis of late antique conceptions on letter speculation, Weiss identifies two main traditions. The first—outlined in chapter 2—resurfaces in rabbinic and hekhalot literature and assumes the creation of the world / seal of the abyss from the ineffable name of God—or, in later articulations, from its specific letters. Within this model—which may be traced back to a Greek/Coptic preference for vowels—the matres lectionis (Hebrew vowels) hold a higher status. Conversely, the second tradition—discussed in chapter 3—conceives the creation of the world from the twenty-two Hebrew letters as a whole and with no hierarchy between vowels and consonants. Completely unattested in rabbinic and hekhalot sources, this second model characterizes Sefer Yeẓirah and a few Syriac Christian grammar writings. The content and linguistic (i.e., same technical terminology) proximity between Sefer Yeẓirah and these sources point to a shared intellectual matrix, “an area in which Greek texts were translated into Syriac and in which Syriac grammar was developed (north Mesopotamia)” (72), possibly seventh-century Edessa or Nisibis.

The second part of the book offers a new understanding of the early reception of Sefer Yeẓirah. Through intelligent analysis of an early gloss to Sefer Yeẓirah and of an excerpt from the epistle of Agobard of Lyon, Weiss demonstrates how the spiritual world of the first readers of the book was equally rooted in midrash, myth, and mysticism (chapter 4). By the ninth century—approximately two centuries after its crystallization and a century before the appearance of its first commentaries—the tradition of Sefer Yeẓirah circulated within the Jewish world even in Europe and was understood in connection with hekhalot literature. This argument is reinforced in chapter 5, where Weiss compellingly interprets a midrash on Sefer Yeẓirah and Ben Sira—copied in the eleventh-century manuscript Vatican 299/4 and given in Hebrew transcription in appendix 3—and discusses Rashi's (1040–1105) approach to the cosmogonic treatise. It emerges that, already before the twelfth century, Sefer Yeẓirah was read as a magico-mystical text and that the tenth-to-twelfth-century philological/scientific commentaries known to us—regarded by scholarship as expression of the only (rabbinic) interpretative direction of the book in this period—were penned in reaction to these early magico-mystical readings.

The epilogue, which stresses the wider implications of Weiss's findings for our understanding of Jewish history, is followed by the two above-mentioned appendices and by the Hebrew transcription of the long version of Sefer Yeẓirah based on Vatican 299/4 and juxtaposed to Peter A. Hayman's English translation (appendix 2).

Extremely accessible and well written, Sefer Yeṣirah and Its Contexts is commendable for its rigorous analysis of primary sources and its remarkable historical sharpness. Fundamental for whoever intends to approach Sefer Yeẓirah from a historical perspective, it is an important reading for students and scholars of Jewish thought, who will be exposed to alternative late antique and medieval Jewish voices. The book has much to add to the growing research on cross-cultural encounters between late antique Judaism and early Syriac Christianity. Similarly, its solid methodology offers interesting insights also for manuscript studies and book history. Weiss's twofold thesis—on the composition and reception of Sefer Yeẓirah—is cogent and opens the way for further research on the interpretation of Jewish texts in light of the rich Syriac literary tradition, on the history of late antique Jewish communities in conversation with Syriac Christianity, as well as on the intellectual world of the early medieval Jews who approached Sefer Yeẓirah (and possibly other canonical books) from a magical perspective.