Summary: Benefits are always attractive when applying for a job, but the benefits of being God's child surpass anything an employer could offer us.
RESULTS OF BEING A SPIRITUAL CHILD
When we stop to think, there are many blessings we receive from our parents. It is the cooperation of the parents in the first place that makes our birth possible. If it were not because of the demonstration of love by a man and woman, you and I would not be here. In the ideal home, the parents supply every need of the child as they grow. They provide food, clothes and a place to stay. They send us to school where we receive an education. They even provide much more than the necessities of life. Some of us grew up in homes with well-to-do parents who could give us a great deal. Others did not have as much. We hopefully experienced love from our parents. We have inherited traits from our parents. We can find characteristics in us that were passed genetically from our parents. Our personality is probably similar to theirs. They were hopefully there for us in our struggles as we grew. Many parents save for their children's college education, or if they do not they pay for it anyway. Many children inherit things from their parents when they die. These may be things they worked and saved most of their life for. When we stop to think about it, there are many advantages of being children of our respective parents.
In like manner, there are some wonderful results that come from being a child of God or a spiritual child of Isaac according to the allegory Paul uses in these verses. Paul continues to contrast the one who tries to work for their salvation with the one who accepts the free grace of Jesus Christ. In these verses, he reaches back into the Old Testament and uses a story to give an analogy. It is not an allegory in the sense that there is some hidden meaning in the story of Abraham, Sarah, Hagar, Isaac and Ishmael. He speaks figuratively. It is an analogous system that Paul uses.
The reason Paul uses this story for his analogy is to further enforce his teaching that salvation is by the grace of God and not our works. He warns the Jewish Christian to look closely at the very law they were placing their faith in for salvation.
I. WE CAN EXPECT GOD'S GUIDANCE
Paul tells the story of Abraham and Sarah and their child Isaac and also of Hagar and Abraham and their child Ishmael. Ishmael was born as a result of a plan by Abraham and Sarah to hurry up what God seemed to be taking too long to do. Hagar was the Egyptian slave of Sarah. Ishmael was not the son of promise. He was the son of the flesh. Isaac was the son of promise that God promised to Abraham and Sarah.
After using the story as an analogy, Paul explains how the heritage of the line through one mother, Hagar, is lostness while the heritage through the other mother, Sarah, is salvation and freedom. You will remember that God called Abraham to leave his homeland and go to a land far away that he had never seen. Here God promised to make him and his descendants great. God promises a son to Abraham through whom these descendants would come. Many years passed, however, and the son was not born. Sarah decided to take matter into her own hands.