even though God had said to him, “Through Isaac your offspring will be reckoned.”
Of whom--rather as Greek "He (Abraham, not Isaac) TO whom it was said" [ALFORD]. BENGEL supports English Version. So Heb 1:7 uses the same Greek preposition, "unto," for "in respect to," or "of." This verse gives a definition of the "only-begotten Son" (Heb 11:17). in Isaac shall thy seed be called-- (Gen 21:12).
Verse 18. Of whom it was said, That in Isaac shall thy seed be called. . A numerous posterity had been promised to him. It was there said expressly that this promise was not to be fulfilled through the son of Abraham by the bond-woman Hagar, but through Isaac.
Accounting that God was able to raise him up, even from the dead,.... Abraham did not go about this affair without thought; and yet he did not consult with flesh and blood; his reasoning was the reasoning of faith; and the conclusion of it was, not that he believed that God would raise his son from the dead, but that he was able to do it.