First, its David talking, not God. Let us be
technical, when you want your Bible to be
technically perfect
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To your question, some context: You are right, there were
several lines of Scriptures. Two became dominant. The Septuagint line (from which Septuagint was translated) and masoretic line.
The Septuagint line was used by universal (Greek speaking) Jewish community, by apostles and by Church (its used by Greek speaking churches till today, without interruption).
Because the Septuagint were so much used by Christians and prophecies about Christ were so clear in it, Jews decided to go by the other, masoretic line, after they made some serious editations to it.
In a reformation era, people in Latin Europe were used to translate from Latin Vulgate. It was unacceptable for reformators, who wanted to get rid of RCC influence. So they decided to translate from original languages, instead.
No problem with the NT. But regarding the OT, there is just one Hebrew line - the masoretic text. Thats why they used it without much consideration - and that was a mistake, IMHO. Greek churches continue in using Septuagint, RCC is probably still using Vulgate? Not sure. So its mainly a protestant problem/issue.
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My response to "which line is correct" - from the historical context, I am very much for the Septuagint line.
1) There is too much Jewish antiChristian agenda behind the masoretic line.
2) The majority of NT places where the OT is quoted is from the Septuagint. So if I want to have a consistent Bible, I must use it.
3) Because it is so massively used in the NT, I think that the authority of apostles and the first Church indicates I should use it too.