Charles Ellicott Commentary Hebrews 8:9

"Not according to the covenant that I made with their fathers In the day that I took them by the hand to lead them forth out of the land of Egypt; For they continued not in my covenant, And I regarded them not, saith the Lord." — Hebrews 8:9 (ASV)

Not according to the covenant.—The difference is declared below (Hebrews 8:10–12). In the day when they were led forth out of Egypt the token of God’s covenant was the deliverance itself. At Sinai, Exodus 24:7–8 , the book of the covenant was read, and the blood of the covenant was sprinkled on the people, who had promised obedience to all the words that the Lord had said.

And I regarded them not.—It is here that the translation departs from the Hebrew, which, as is now generally believed, is faithfully represented in our Authorised Version: although I was a husband to them (that is, had the authority of a husband). The quotation here follows the LXX. without change.