Jesus would be the Promised Seed of Isaac.

Prophecy: "But God said, Sarah your wife shall bear you a son indeed; and you shall call his name Isaac (laughter), and I will establish My covenant or solemn pledge with him for an everlasting covenant, and with his posterity after him" (Genesis 17:19).

...It is through Isaac that your offspring will be reckoned" (Genesis 21:11 NIV).

Fulfilment: "And Abraham was the father of Isaac..." (Matthew 1:2).

"For Sarah became pregnant and bore Abraham a son in her old age, at the set time God had told him" (Genesis 21:2).