On a certain day Abram was going about his business as usual when God came to him out of the blue…
When Abram was ninety-nine years old, the Lord appeared to him and said, “I am God Almighty; walk before me faithfully and be blameless. Then I will make my covenant between me and you and will greatly increase your numbers.” (17:1-2)
For the first time in the relationship, God is giving Abram covenant terms (conditions) that he must follow, beginning in verse 1 with “walk before me faithfully and be blameless.” In the next several verses (3-8) God promises Abram that he will not only have a son, but that he will be the father of many nations, and changes his name to Abraham. As the father of nations, he will also be the ancestor of kings, and God’s covenant will extend to all of Abraham’s descendants, and those of his entire household. The land of Canaan will be their homeland and they will take possession of it, something Abram had not yet been able to do. There is another condition as well, for all males must be circumcised.
In 17:9-14 God makes it abundantly clear that each and every male must be circumcised as a sign of the covenant, including anyone in the household who is not a blood relation and that if they do so, God will be their God, and the God of their descendants. If they do not do so, they are to be cast out.
Sarai is also to be blessed, for she in spite of their ages, will bear a son through whom the covenant will pass to future generations; her name was changed to Sarah. Abraham’s reaction was to laugh, for how could they produce children at their ages? He suggested that Ishmael could be the son through whom the covenant would pass, but God, while willing to bless Ishmael with a great nation of his own, insisted that Abraham and Sarah would have the Son of Promise; they would name him Isaac, and he would be born within the year. To his everlasting credit, Abraham stopped laughing and was circumcised on that very day, along with all of the males in his household.
Let’s take just a moment and ask ourselves a simple question: Why did God wait around until Abraham was 99 and Sarah was 90 to fulfill His promise to give them a son − was He too busy in another galaxy or something?
While we’re asking ourselves questions, let’s ask another one: Why did the Son of God come to earth as an infant born to a teenager in a manger in Bethlehem instead of coming on the wings of angels into downtown Jerusalem?
I can suggest one answer: God’s power is best seen when the humans in the picture are weakest. Certainly a son born to a 90 year old, fathered by a 99 year old is just as unlikely as a child born to a virgin, for as we know, both are not possible in the normal course of events.
In both cases there would be no doubt that God Himself was responsible for the birth of a promised son.