Paul may have quoted from the Septuagint, however... Most of Christ's "on foot" ministry was done to the Jews... There's no indication he ever used Greek but plenty, growing up as a Jew, he had the Hebrew texts memorized and quoted to them in their own language. Regardless...
As you state the Septuagint is the Greek translation of the Hebrew text.
The Masoretic text is simply... The best Hebrew text we have.
Now, what do you suppose would generally maintain the most accuracy?
Hebrew- Greek- Hebrew
or
Hebrew
????
I realize your argument but honestly if we can't have faith in what we've got written- we're in trouble. We need to have faith that what we've got is the best representation around.
Additionally in researching Isaiah 53, I find the Great Isaiah Scroll (Hebrew, containing much of Isaiah- I'm sure you heard of it) matches the Masoretic text- even being 1,000 years removed from each other. The Septuagint is the odd man out. Translators know this- that's why they didn't use the one minority translation.
Regardless, again, we need to have faith in what we've got. I've seen you use this argument before. One can't run to a different text simply because you don't like what's there.
My friend, do the research, the text you are using is from approximately 900 to 1000 years "After" Christ. The Septuagint is approximately 200 years "Before" Christ. it was translated by the Jews and was the Jewish Scriptures. The reason the Jews rejected it was because the Christians were using it to prove that Jesus was the Christ. It is not a minority translation, it was "The" Bible in the days to Jesus and the apostles, and yes they did quote from it. Jesus may have used Hebrew in Jerusalem, but at that time it was not widely spoken, Greek was.
Concerning the Isaiah scroll, consider where today's Masoretic text differs from the Septuagint and see which one the Isaiah Scroll lines up with.
Regarding the accuracy of the translation. The Septuagint was not translated back into Hebrew as you suggested above. The Septuagint was also translated from a different text family than the Masoretic text we have today. However, one only needs to look at the Scriptures to see that the Masoretic text is different than the what Jesus and the apostles used. Look at some of the quotes in the NT and compare them in the OT. You will many differ, not all because in many places the Septuagint and the Masoretic text read alike, but where they differ Jesus and the apostles used the Septuagint. I am including a few verses for consideration there are many more than this.
Below are several New Testament quotes, I have given the corresponding verses in the Old Testament, from both the Masoretic text which is the text used in almost all of the current English Bibles, and the Septuagint or the LXX, which is the Greek text used in the time of Christ. Notice how the Masoretic text does not follow the New Testament quotes as the Septuagint does. This is just a few, there are a lot more.
New Testament
Hebrews 1:6 ( KJV ) 6And again, when he bringeth in the firstbegotten into the world, he saith, And let all the angels of God worship him.
The writer of Hebrews quotes this verse from Deuteronomy 32:43
Masoretic text
Deuteronomy 32:43 ( KJV ) 43Rejoice, O ye nations, with his people: for he will avenge the blood of his servants, and will render vengeance to his adversaries, and will be merciful unto his land, and to his people.
Where are the words, "And let all the angels of God worship him"?
Septuagint
Deuteronomy 32:43 Rejoice, ye heavens, with him, and let all the angels of God worship him; rejoice ye Gentiles, with his people, and let all the sons of God strengthen themselves in him; for he will avenge the blood of his sons, and he will render vengeance, and recompense justice to his enemies, and will reward them that hate him; and the Lord shall purge the land of his people.
New Testament
Hebrews 10:5 ( KJV ) 5Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me:
The writer of Hebrews quotes this verse from Psalm 40:6
Masoretic text
Psalms 40:6 ( KJV ) 6 Sacrifice and offering thou didst not desire; mine ears hast thou opened: burnt offering and sin offering hast thou not required.
Where are the words, " but a body hast thou prepared me:"? This is an important part to leave out since it speaks of the incarnation of Christ.
Septuagint
Psalms 40:6 Sacrifice and offering thou wouldest not; but a body hast thou prepared me: whole-burnt-offering and sacrifice for sin thou didst not require.
New Testament
1 Peter 4:18 ( KJV ) 18And if the righteous scarcely be saved, where shall the ungodly and the sinner appear?
Peter quotes Proverbs 11:31
Masoretic text
Proverbs 11:31 ( KJV ) 31Behold, the righteous shall be recompensed in the earth: much more the wicked and the sinner.
Septuagint
Proverbs 11:31 If the righteous scarcely be saved, where shall the ungodly and the sinner appear?
New Testament
Matthew 3:3 ( KJV ) 3For this is he that was spoken of by the prophet Esaias, saying, The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight.
Here Mtthew quotes Isaiah 40:3
Masoretic text
Isaiah 40:3 ( KJV ) 3The voice of him that crieth in the wilderness, Prepare ye the way of the LORD, make straight in the desert a highway for our God.
Septuagint
Isaiah 40:3 The voice of one crying in the wilderness, Prepare ye the way of the Lord, make straight the paths of our God.
New Testament
James 4:6 ( KJV ) 6But he giveth more grace. Wherefore he saith, God resisteth the proud, but giveth grace unto the humble.
Here James quotes Proverbs 3:34
Masoretic text
Proverbs 3:34 ( KJV ) 34Surely he scorneth the scorners: but he giveth grace unto the lowly.
Septuagint
Proveerbs 3:34 The Lord resists the proud; but he gives grace to the humble.
New Testament
Matthew 15:7-9 ( KJV ) 7Ye hypocrites, well did Esaias prophesy of you, saying, 8This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me. 9But in vain they do worship me, teaching for doctrines the commandments of men.
Here Jesus quotes from Isaiah 29:13
Masoretic text
Isaiah 29:13 ( KJV ) 13Wherefore the Lord said, Forasmuch as this people draw near me with their mouth, and with their lips do honour me, but have removed their heart far from me, and their fear toward me is taught by the precept of men:
Septuagint,
Isaiah 29:13 And the Lord has said, This people draw nigh to me with their mouth, and they honour me with their lips, but their heart is far from me: but in vain do they worship me, teaching the commandments and doctrines of men.
New Testament
Matthew 21:16 ( KJV ) 16And said unto him, Hearest thou what these say? And Jesus saith unto them, Yea; have ye never read, Out of the mouth of babes and sucklings thou hast perfected praise?
Masoretic text
Psalms 8:2 ( KJV ) 2 Out of the mouth of babes and sucklings hast thou ordained strength because of thine enemies, that thou mightest still the enemy and the avenger.
Septuagint,
Psalms 8:2 Out of the mouth of babes and sucklings hast thou perfected praise, because of thine enemies; that thou mightest put down the enemy and avenger.