Recent scholarship on the history of the biblical canons has increasingly recognised that the Jewish and Christian Bibles were not formed independently of each other but amid controversial debate and competition. But what does it mean that the formation of the Christian Bible cannot be separated from the developments that led to the Jewish Bible? The articles in this collection start with the assumption that the authorization of writings had already begun in Israel and Judaism before the emergence of Christianity and was continued in the first centuries CE by Judaism and Christianity in their respective ways. They deal with a broad range of sources, such as writings which came to be part of the Hebrew Bible, literature from Qumran, the Septuagint, or early Jewish apocalypses. At the same time they deal, for example, with structures of authorization related to New Testament writings, examine the role of authoritative texts in so-called Gnostic schools, and discuss the authority of late antique apocryphal literature.