John Calvin Commentary Genesis 25:12

"Now these are the generations of Ishmael, Abraham`s son, whom Hagar the Egyptian, Sarah`s handmaid, bare unto Abraham." — Genesis 25:12 (ASV)

Now these are the generations of Ishmael. This narration is not unnecessary. In the beginning of the chapter, Moses alludes to what was done for the sons of Keturah. Here he speaks intentionally in more detail to show that the promise of God, given in the seventeenth chapter (Genesis 17:1–22), was confirmed by its clear fulfillment.

In the first place, it was no ordinary gift from God that Ishmael had twelve sons who possessed rank and authority over as many tribes. But since the event matched the promise, we must primarily consider the truthfulness of God, as well as the remarkable benevolence and honor He showed toward His servant Abraham. Even in those benefits that were merely supplementary, He treated him so kindly and generously. For that which was added to the spiritual covenant may rightly be regarded as supplementary.

Therefore, after Moses has listed the towns where Ishmael's descendants settled, he consigns that entire lineage to obscurity, so that lasting continuity might remain only in the Church, according to the declaration in Psalm 102:28, the sons of sons shall inhabit.

Furthermore, Moses, as if pointing with his finger, shows the wonderful plan of God: by assigning the sons of Ishmael a region separate from the land of Canaan, He both provided for their future and kept the inheritance open for the sons of Isaac.