The NT leans very heavily on Habakkuk 2:4 and it is clear that it is not looking at the Hebrew, which reads like this:
[Rom 1:17 NKJV] (17) For in it the righteousness of God is revealed from faith to faith; as it is written, "The just shall live by faith."
[Gal 3:11 NKJV] (11) But that no one is justified by the law in the sight of God is evident, for "the just shall live by faith."
[Heb 10:38 NKJV] (38) Now the just shall live by faith; But if anyone draws back, My soul has no pleasure in him."
Here is the Masoretic Hebrew based Habakkuk:
[Hab 2:4 NKJV] (4) "Behold the proud, His soul is not upright in him; But the just shall live by his faith.
So it is clear to me that the NT authors were working from the Greek.
But there are also key differences between the NT Greek and the LXXs that I have. There is the matter of word order in Hebrews 10:38 but much more importantly is the fact that Habakkuk has μου after πίστεώς.
[Hab 2:4 LXX] ἐὰν ὑποστείληται οὐκ εὐδοκεῗ ἡ ψυχή μου ἐν αὐτῷ ὁ δὲ δίκαιος ἐκ πίστεώς μου ζήσεται
[Hab 2:4 Brenton] If he should draw back, my soul has no pleasure in him: but the just shall live by my faith.
If I remove ἐκ πίστεώς μου I get "...but the just shall live."
What does that clause add? Does it say that "...the just shall live by my faith"? Or is it, "...the just owing to my faith shall live"?
I also posted this here: