The Septuagint

The Septuagint is a Greek translation of the Hebrew Scriptures. It was commissioned by an Egyptian Pharaoh who wanted to promote learning. At the time (3rd century BC), Alexandria was a center of learning, and it would continue to be for several centuries. Alexandria also had a sizeable Jewish population, and so Pharaoh Ptolemy Philadelphus commissioned a Greek translation that commenced somewhere around 250 BC.
The story of the translation of the Septuagint is told by some famous people. Philo of Alexendria and Josephus, two famous Jewish writers from the time of Jesus, both tell the story I'm about to tell you. It's repeated by at least Justin Martyr (AD 150) as well as other early Christians.
As the story goes, the Pharaoh wanted an honest, excellent translation, so he sent to Israel to get their best scholars. Seventy-two scholars showed up to translate the Law of Moses, and he put them all in separate cells. Despite the separation, they produced 72 translations that were word-for-word the same.
I'm not telling you this story is true. I'm telling you a lot of people believed it, such as:
By the first century a lot of Jews, especially outside Jerusalem, were more Greek-speaking than Hebrew-speaking. Many of them, like Philo and Josephus, believed the story about the translation of the Septuagint, and thus they thought the Septuagint was an inspired translation. Many early Christians agreed.
By the time of Jesus all the Hebrew Scriptures (the whole Old Testament) had been translated into Greek, not just the Law of Moses, and churches, who were mostly Greek-speaking, used the Septuagint as their primary Bible, considering it inspired.
The term Septuagint means "the translation of the 70," and as a result it is also called the LXX (Roman numerals for 70).
Most of the quotations found in the New Testament are from the Septuagint rather than the Hebrew texts from which our modern English Bibles are translated. I found an awesome quote on the internet showing the agreement of scholars, Catholic and Protestant, about how much the Septuagint is quoted in the New Testament. (I'm using asterisks to help set off the quote.)
***Of the places where the New Testament quotes the Old, the great majority are from the Septuagint version. Protestant authors Archer and Chirichigno list 340 places where the New Testament cites the Septuagint but only 33 places where it cites from the Masoretic Text rather than the Septuagint (G. Archer and G. C. Chirichigno, Old Testament Quotations in the New Testament: A Complete Survey, 25-32).***
This paragraph is found on a Catholic web site (http://www.catholic.com/quickquestions/in-which-passages-does- jesus-quote-the-septuagint-and-where-does-the-new-testament-al), and it is written by a scholar who graduated from a Franciscan university. Yet here he is able to appeal to Protestants to justify his statement that it is the Septuagint that is primarily quoted by the New Testament authors.
One notable example is Jesus rebuke of Pharasaic tradition. Part of the quote from Isaiah that he uses is "in vain do they worship me, teaching for commandments the traditions of men" (Mark 7:6-7). That passage is found only in the Septuagint of Isaiah 29:13.
THE LXX AND PROPHECY
The Christians proved so adept at using the prophecies in the Septuagint that Jewish leaders stopped using it and began claiming that it had errors. They switched to a Hebrew text and claimed that it was pure. In return, second century Christians began accusing Jews of changing Scripture to hide the prophecies of the Messiah because they predicted Jesus and his crucifixion too accurately.
The Jews managed to win at least one Christian over to that idea, but not until early in the fifth century (the 400's). Jerome made a Latin translation of the Scriptures in the early fifth century because a lot of the western Roman empire had been speaking Latin primaritly for a couple centuries.
That translation is called the Vulgate, and it managed to become the Bible of choice in the west.
The western empire, including Rome and north Africa fell to Barbarians later in the fifth century. The eastern empire, with a capital at Constantinople, continued for another thousand years, still speaking Greek and still using the Septuagint. To this day, it is still the Bible of most of the Orthodox branches of Christianity.
This article only brushes the surface of the history of the Septuagint, but I do want to cover one more thing.
Somewhere along the line, the Jews began a very careful campaign to ensure the accuracy of their Hebrew manuscripts. A group (or a family?) called the Masoretes began keeping strict rules when they copied manuscripts, even counting the number of characters on a page, making sure they were an exact match.
Nonetheless, the oldest Masoretic text we have comes from the 9th century. Thus, to scholars, when it comes to determining the most accurate text, there is a choice between a Greek translation of a Hebrew text dating to the couple centuries before the birth of our Lord or a Hebrew text that cannot be proved accurate until the 9th century. That's a tough choice.

It's a slow process, but more and more Protestants are moving to reading English translations of the Septuagint. The differences aren't great, but some are important. There are seven different chapters in the book of Jeremiah, and the Dead Sea Scrolls backed up the Septuagint version of that book. One other interesting thing is that the Septuagint of 2 Samuel clears up a difficulty concerning Saul's recognition of David when he volunteered to kill Goliath.