Hebrews 8:9 "they continued not in my covenant, AND I REGARDED THEM NOT, saith the Lord."
Jeremiah 31:32 "which my covenant they brake, ALTHOUGH I WAS AN HUSBAND UNTO THEM, saith the LORD."
John Owen's Commentary on the book of Hebrews.
https://www.studylight.org/commentaries/joc/hebrews-8.html
"But expositors do find or make great difficulties herein. It is generally supposed that the apostle followed the translation of the LXX., in the present copy whereof the words are so expressed. But how they came to render בָּעַלתּי by ἠμέλησα, they are not agreed. Some say the original copies might differ in some letters from those we now enjoy.
But the best of these conjectures is uncertain, and some of them by no means to be admitted. UNCERTAIN IT IS THAT THE APOSTLE MADE ANY OF HIS QUOTATIONS OUT OF THE TRANSLATION OF THE LXX.; yea, the contrary is certain enough, and easy to be demonstrated. Neither did he write this epistle unto the Hellenistical Jews, or those who lived in or belonged unto their dispersions, wherein they made use of the Greek tongue; but unto the inhabitants of Jerusalem and Judea principally and in the first place, who made no use of that translation. HE EXPRESSED THE MIND OF THE SCRIPTURE AS HE WAS DIRECTED BY THE HOLY GHOST, IN WORDS OF HIS OWN. And the coincidence of them with those in the present copies of the LXX. hath been accounted for in our Exercitations. * [See below for Owen’s notes in his Exercitations]
The apostle neither in this nor in any other place doth bind up himself precisely unto the translation of the words, but infallibly gives us the sense and meaning; and so he hath done in this place. For whereas בַּעַל signifies a “husband,”…IT IS AS MUCH AS “I EXERCISED THE RIGHT, POWER AND AUTHORITY OF A HUSBAND TOWARDS THEM; I DEALT WITH THEM AS A HUSBAND WITH A WIFE THAT BREAKETH COVENANT: “THAT IS, saith the apostle, “I REGARDED THEM NOT” WITH LOVE, TENDERNESS, AND AFFECTION OF A HUSBAND.” So he dealt indeed with that generation which so suddenly brake covenant with him...And this manifests the meaning of the preceding words to be God’s severity towards them: ‘I USED THE AUTHORITY OF A HUSBAND, I REGARDED THEM NOT AS A WIFE ANY MORE, saith the Lord.”
John Owen - "the LXX - IF ANY SUCH LXX THERE WERE"
In his massive exposition of Hebrews, John Owen makes some interesting observations regarding the relationship of the book of Hebrews to the LXX. He was well schooled in Greek, Hebrew, Latin, and Syriac. He possessed a vast knowledge of manuscripts and other translations. In his work on the book of Hebrews, Owen discusses each passage in great detail about the Hebrew and Greek, along with comments about the LXX translations done by Aquila, Theodotian, and Symmachus. (These last three men mentioned each attempted a Greek translation of the O.T. after the N.T. was already completed. Today, there is little left of their writings, but we know that they all three differed from each other.)
In his commentary, John Owen makes this amazing statement: "It is evident that they are exceedingly mistaken who affirm that the apostle cites all his testimonies out of the translation of the LXX, as we intimated is by some pleaded... Should he [Paul] have had any respect unto that translation [LXX], it were impossible to give any tolerable account whence he should so much differ from it almost in every quotation, as is plain that he doth... And thus, in those testimonies where there is a real variation from the Hebrew original, THE APOSTLE TOOK NOT HIS WORDS FROM THE TRANSLATION OF THE LXX, BUT HIS WORDS WERE AFTERWARDS INSERTED INTO THAT TRANSLATION... Whereas the reasons of the apostle for his application of the testimonies used by him in his words and expressions are evident, as shall in particular be made to appear, so no reason can be assigned why THE LXX - IF ANY SUCH LXX THERE WERE - who translated the Old Testament, or any other translators of it, should so render the words of the Hebrew text." Exposition Of Hebrews, Vol I, Exercitation V. (CAPS are mine)
Related topics -
The "QUOTES" in Scripture, the so called Greek Septuagint and the phrase “IT IS WRITTEN”