Michael D. Coogan, The Old Testament: A Historical and Literary Introduction to the Hebrew Scriptures, third edition (Oxford University Press, 2014), 7.
A necessary first stage in the study of the Bible is to determine what its actual text is. This is immensely difficult, because thousands of manuscripts need to be compared. Moreover, even before the Jewish canon was established, many of the books that eventually ended up in it were being translated into other languages, so that those who no longer understood Hebrew could still read the sacred texts. The earliest of these ancient translations is in Greek and is known as the Septuagint, from the word for “seventy,” because according to legend some seventy translators of the Torah independently produced identical translations, thereby proving that the translation was as inspired as the original. We should assume that, like the scribes who copied Hebrew manuscripts, the Septuagint translators wanted to be as faithful as possible to the text in front of them. So studying ancient translations like the Septuagint is another path to the original. Again, however, we no longer have the first Septuagint manuscript but only copies, so these too must be compared, both with each other and with Hebrew manuscripts. Besides, translation involves interpretation, not just copying, and Hebrew and Greek words often have different nuances, so it is often uncertain what the Hebrew behind the Greek was. All this is also true of translations into other ancient languages, such as Aramaic and Latin.
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