THE PROMISE SEALED WITH AN OATH

. And the angel of the LORD called unto Abraham out of heaven the second time,
And said, By myself have I sworn, saith the LORD, for because thou hast done this thing, and hast not withheld thy son, thine only son:
That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies;
And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.

THE BIRTH OF ISAAC

The LORD graciously remembered and visited Sarah as He had said, and the LORD did for her as He had promised.
So Sarah conceived and gave birth to a son for Abraham in his old age, at the appointed time of which God had spoken to him.
Abraham named his son Isaac (laughter), the son to whom Sarah gave birth.