The Septuagint (also known as the LXX) was translated from the Ancient Hebrew Text a century or more before the Incarnation. By the time of the Incarnation, Ancient Hebrew (the language of Moses and the Patriarchs) was a dead language. From every indication, the original Ancient Hebrew Text did not survive the A.D. 70 destruction of Jerusalem; no copy, nor even a fragment, is known to be extant. The LXX was used by Jews as well as Christians. The Greek dialect of the LXX, Koine, is the same Greek dialect in which the Apostles penned the Gospel Accounts and the Epistles.
Because of the regrettable precedent set by William Tyndale (who should have translated from the LXX), the Masoretic Hebrew Text has been the source from which pre-Incarnation Scripture in almost every English Bible has been translated. But the Masoretic Hebrew Text was unknown until its publication in the Fifteenth Century of the present Christian era. From every indication, the Masoretic Hebrew Text is a forgery which is a translation from the LXX into Masoretic Hebrew, but with many corruptions. Christian scholars in the Fifteenth Century declared the Masoretic Hebrew Text a counterfeit.
In Romans 3:1-2, the term "Jew" means "one who has covenantal relationship under the Old Covenant." Once the Old Covenant was dissolved by the death of Jesus in the role of Husband of Israel, the "Jew" no longer was qualified to be custodian of the Scripture. Custodianship of the Scripture passed to the Church, which enjoys covenantal relationship under the New Covenant.
The Jews who created the Masoretic Hebrew Text lived in the present Christian era. Thus, they no longer enjoyed covenantal relationship under the Old Covenant, and, being unregenerate, they certainly did not enjoy covenantal relationship under the New Covenant. Thus, the oft-repeated Legend of the Faithful Masorete Scribes is a fraud; the Masoretes were counterfeiters who had no authorization to handle the Scripture.
When the writers of the Gospel Accounts and the Epistles cite the Scripture, the reading of the citation typically agrees with the reading of the LXX and typically disagrees with the reading of the Masoretic Hebrew Text. The citations by Jesus and the Disciples authenticate the LXX as the official text of Scripture written prior to the Incarnation. Inasmuch as the Lord God is not the author of confusion, I Corinthians 14:33, it is unthinkable that he should allow the existence of two authoritative texts of Scripture; this explains the disappearance of the Ancient Hebrew Text.
The Masoretic Hebrew Text and knowledge of the Masoretic Hebrew language is of no value to the Christian. The motto of the Christian regarding the Scripture should be, "It's all Greek to me."