John Calvin 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, etc. Here is expressed the difference between the covenant that then existed and the new one that He led them to expect. The Prophet might have otherwise said only, “I will renew the covenant which through your fault has come to nothing”; but he now expressly declares that it would be one unlike the former. By saying that the covenant was made on the day when He took them by the hand to rescue them from bondage, he enhanced the sin of defection by thus reminding them of such a great benefit. At the same time, he did not accuse only one age of ingratitude; for as these very men who had been delivered immediately fell away, and as their descendants after their example continually relapsed, thus the whole nation had become covenant-breakers.

By saying that He disregarded them or had no regard for them, he intimates that it would profit them nothing to have once been adopted as His people, unless He helped them by this new kind of remedy. At the same time, the Prophet expresses in Hebrew something more; but this has little to do with the present question.