Genesis 17:18.
Abraham asked God to accept Ishmael ...since he is old and didn't think he'll bear anymore children especially with Sarai who is 90 already. But God keeps his promises...or more to the fact his “covenant”. Therefore, it is the child from his “legal wife” will the true promised child come forth. It is a sample of God's mighty power and of him being outside of time. Since he can make Sarai...a 90 year old woman still bear a child.
I remember a guest in The Journey Home program, he is a Muslim convert. He said to this effect, “How can Ishmael be the promised child? His mother Hagar is of bearing age while Sarah is not. And yet she was able to bear Isaac. Between Isaac and Ishmael, who is the miracle child?”
Also, God is still merciful to Ishmael. A child is a child. Every child is provided for by God. It was not the child's fault. Hagar was given to Abram by Sarai and thus he was conceived. The problem is the arrogance of Hagar.
Genesis 17:9-11.
I wondered why circumcision is the physical sign God had chosen? In the CCB commentary, it said, “such was the practice in the Orient at the time for fertility”. Maybe it's God's way of changing a pagan rite into something more meaningful. They do it anyway, so let it be done for Him. In a way, it is like when the Church has the authority to change (or replace) pagan rituals to Christian ones. Oh, yeah, if such a practice in the Orient is for fertility… maybe that is God’s way of saying “be fruitful and multiply”… he did promise Abraham that his children will as many as the stars.
Get a load of this … Since God made Abraham have his household circumcised, as a sign of covenant with Him, then wouldn’t it be the same for baptizing a household? From the babies to the eldest would be baptized? So why are Protestants so opposed to infant baptism? We are baptized to become children of God. Do they mean to deny babies to be come children of God just because they can’t profess their faith? Of course I’m citing this because it could be a good defense of our faith
when questioned about infant baptism … but then again … I’m not a theologian