This post is part of an ongoing series comparing the Hebrew Masoretic text with the Greek Septuagint.
Below are excerpts from a lecture series on the Masoretic text of the Hebrew Bible by Jewish scholar, Professor Emanuel Tov, published on the website theTorah.com. Professor Tov is J. L. Magnes Professor of Bible (emeritus) in the Dept. of Bible at the Hebrew University of Jerusalem:
Before the mid-20th century, many scholars divided the texts of the Hebrew Bible into three text types: the Masoretic Text (MT), the Samaritan Pentateuch (SP), and the LXX. Between 1947 and 1956, however, many biblical scrolls dating back to the Second Temple Period were uncovered in the caves of Qumran that did not fit into this neat three-version pattern. These scrolls, belonging to the sect of Jews who lived in the area, display broad textual diversity.
|Map of the Judean Desert|
In contrast, twenty-five texts were found in the Judean Desert at sites other than Qumran, and these display almost complete identity (roughly 98% agreement) in consonants with the medieval Masoretic text as reflected in the Leningrad Codex, the earliest complete version of MT. Thus, the consonantal text of MT was in existence more than a thousand years before the creation of MT. Scholars usually designate this consonantal base of the Masoretic Text as proto-Masoretic although sometimes also, anachronistically, as the Masoretic Text.
The non-Qumran Judean Desert scrolls were found at both the earlier site of Masada (texts written between 50 BCE and 30 CE)  and the later sites of Wadi Murabba‘at, Wadi Sdeir, Naḥal Ḥever, Naḥal ‘Arugot, and Naḥal Se’elim, dating to the period of the Bar Kochba revolt in 132–135 CE.
…The relationship between MT and the ancient Judean Desert texts is one of almost complete identity showing that the consonantal framework of MT changed very little over the course of one thousand years—the period between the scrolls and the earliest medieval codices.