Heb 11:20

By faith Isaac blessed Jacob and Esau, even regarding things to come.

Isaac was the child of the Promise.
The child born to Abraham and Sarah when they “were as good as dead”…well past child-bearing age.

The Lord will fulfill His Word…in His time…

Gen 21:1-5

Then the LORD took note of Sarah as He had said, and the LORD did for Sarah as He had promised.

So Sarah conceived and bore a son to Abraham in his old age, at the appointed time of which God had spoken to him.

Abraham called the name of his son who was born to him, whom Sarah bore to him, Isaac.

Then Abraham circumcised his son Isaac when he was eight days old, as God had commanded him.

Now Abraham was one hundred years old when his son Isaac was born to him.

The Lord took note.
The Lord did for Sarah as He promised.
At the appointed time.

Abraham walked in obedience in circumcising his son.

This Promised One was the beginning of the great hosts of descendants promised by the Lord.

Despise not the days of small beginnings. What is the Lord doing today in you?

Zec 4:10

“For who has despised the day of small things? But these seven will be glad when they see the plumb line in the hand of Zerubbabel—these are the eyes of the LORD which range to and fro throughout the earth.”