There is no reason to delay in carrying out the will of God once we are certain of it. Any delay shows either an unwillingness to obey or failure to appreciate the greatness of the Lord and his authority over us. We obey God even when we do not fully understand why he commands us to do what he does. Obedience will shed further light on the command in time, and we will learn more later from our own obedience to what he commands us to do.
We have covered a vital period of history in the family of God, in Abraham's family. We have seen the culture solution was a disaster; we have seen the prophecy from God that the separation would be renewed. It has been a long wait for a seed, 25 years. Why did God cause them to wait 25 years for the seed? Why did they have to wait until they were ancient, and every year that went by it seemed more difficult to believe that the promise would ever be fulfilled? It is a lesson we too have to learn. Very often we receive answers to our prayers at once, but God's will is that for all of us there will be some things for which our faith has to be proved and tested; it has to mature and deepen. So God will encourage you with many rapid answers to prayer, but some things you will have to wait and keep your trust, because ultimately, if you are a believer, your faith is an expression of your love. Your faith measures your love. Trust him, ask him for more trust. It is a form of worship; God receives it. God welcomes your love and your faith and you glorify him. So there must be no shortcuts for us as individuals, or as a church. However long things take, we trust the Lord, and we prove him.
Why was Ishmael circumcised if he was not in the covenant? Abraham was instructed to circumcise all who were in his household, even Ishmael, but God knew that Ishmael was soon to be sent away, so why was he included? Ishmael would not inherit the land, but Isaac would. Ishmael and his descendants did not receive the promises that were given to Abraham, Isaac, and Jacob, that their seed would be as numerous as the stars in the heavens and the sand on the seashore, but that promise came to Isaac. If circumcision was a sign of membership of the covenant, as Genesis 17:10 indicates, then was it not inappropriate to give it to one who was explicitly shut out of the covenant? Paedobaptists use the case of Ishmael to argue that it is right to baptize infants even if they never come to faith, but this is a serious mistake. Not only is baptism an ordinance associated with the new birth, not with natural birth, and therefore should not be applied to infants at all, but furthermore Ishmael does not give us a pattern that we should follow. He stands for all those who fall short of salvation, and who are only ever outward members of covenant. Those of Abraham’s descendants who enjoyed the outward privileges of the covenant but who lacked faith, were never really under grace, and were as a result treated as under the law at Sinai. They had to learn that without faith, membership of the Abrahamic covenant had not changed their relationship with God. Ishmael is a type of those who fail to believe the promises, and yet have some external attachment to the covenant. He represents unbelieving Jews. They enjoyed the external privileges of the covenant but came short of salvation. Ishmael did not even get this far. He received circumcision, but failed to enjoy even the outward privileges which the descendants of Abraham were given. In the language of the type he fell short in an even more marked way. In Galatians Paul points to Hagar and her child, Ishmael, as representing those who are still in bondage because they are under the law: that it, Ishmael is a type of the unbelieving Jew.