Judaism is a religion of the book. When and where did that begin to be the case? The various historic Christian churches treasure various collections of Jewish writings. Why is that?
A collection of authoritative religious texts may have begun to be assembled early, in the 6th century BCE, among Judahite refugees in Babylon. By the 2nd century BCE, the development of a canon of authoritative texts was in full swing among those who saw themselves as heirs to the promises that are found in the Torah, the Prophets, and David.
In the first centuries of the current era, across the lands and languages of the countries in which first Jews and then Jews and Christians resided, the inner core but not the outer edges of a canonical collection to which all might appeal was widely acknowledged.
This meant that when Jews of diverse provenance became Christians they brought with them the collection of texts their community of origin treasured.
Some collections were more extensive than others. To this day, therefore, an Old Testament canon of identical breadth is not found among Christians. At the same time, a common core is readily identifiable: the Torah, the Prophets, and the Writings of rabbinic fame, identical to the Old Testament as defined by the churches of the Reformation.
For a brief introduction to the canon of the Hebrew Bible and three historic canons of the Old Testament, go here.