In this study I examine the linguistic and theological contours of the term ( torâ ) in Ezra-Nehemiah—particularly the identification of with the law () of God promulgated by Ezra (Ezra 7:14)—through the lens of Old Persian and Avestan notions of "the law set down ( dāta )" by Ahura Mazda and revealed through Zarathustra. While the basic notion of divine revelation of laws through the mediation of Moses emerges already in preexilic biblical texts, I posit that the innovative link drawn by the authors of Ezra-Nehemiah between the Old Persian and Avestan term dāta (via Aramaic ) and the Hebrew reflects a broader and more comprehensive impact of Avestan traditions, mediated by Achaemenid ideology, on the construction and conceptualization of Mosaic in Ezra-Nehemiah. Weighing in on the ongoing debate over the range of imperial authorization of local legislation and cult in Judea, Egypt, and Asia Minor, I argue that the Achaemenids, who were probably involved in certain aspects of the codification and canonization of textual, legal, and theological manifestations of Zoroastrianism, functioned as agents (whether actively or passively) in facilitating and reinforcing the adaptation by the Babylonian-Judean scribes of Avestan notions of divine revelation of the law and scriptural unity linked to personal authority.