And the angel of the LORD called to Abraham from heaven a second time,
15. And the angel of the Lord called unto Abraham . What God had promised to Abraham before Isaac was born, he now again confirms and ratifies, after Isaac was restored to life, and arose from the altar, — as if it had been from the sepulcher, — to achieve a more complete triumph.
Abraham's obedience was graciously accepted; but this was not all: here we have it recompensed, abundantly recompensed, before he stirred from the place; probably while the ram he had sacrificed was yet burning God sent him this gracious message, renewed and ratified his covenant with him. All covenants were made by sacrifice, so was this by the typical sacrifices of Isaac and the ram.
Commenting on Genesis 22:15-19
And the Angel of the Lord called unto Abraham out of heaven the second time. The Angel having restrained him from slaying his son, and having provided another sacrifice, which he offered, calls to him again; having something more to say to him, which was to renew the covenant he had made with him, and confirm it by an oath.