John Calvin Commentary Deuteronomy 7:8

"but because Jehovah loveth you, and because he would keep the oath which he sware unto your fathers, hath Jehovah brought you out with a mighty hand, and redeemed you out of the house of bondage, from the hand of Pharaoh king of Egypt." — Deuteronomy 7:8 (ASV)

Because he would keep the oath. The love of God is here referred back from the children to the fathers. For he addressed the men of his own generation when he said that they were therefore God’s treasure, because He loved them. Now he adds that God had not just begun to love them for the first time, but that He had originally loved their fathers when He chose to adopt Abraham, Isaac, and Jacob.

But although he more clearly proves that the descendants of Abraham had deserved nothing of the kind because they are God’s peculiar people only by right of inheritance, still it must be remarked that God was induced to be kind to Abraham by no other cause than mere generosity.

A little further on, therefore, he will say that those who then survived were dear to God because He had already loved their fathers. But now he still further commends the goodness of God because He had handed down His covenant from the fathers to the children, to show that He is faithful and true to His promises. At the end of the verse, he teaches that the deliverance of the people was both an effect and a testimony of that grace.