So God was with the lad; and he grew and dwelt in the wilderness, and became an archer. He dwelt in the Wilderness of Paran; and his mother took a wife for him from the land of Egypt. (Gen 21,20-21)

A person moves through life on a trajectory that is determined by his or her strongest character traits. We can imagine them physically as forces that impact an object and make it move in a certain direction, or, more poetically, as strings that pull a person somewhere, often without him being directly aware of it. Since these are features of his own nature, it seems quite natural to him that his path turns wherever he is drawn.

Once a man comes to know God, many things change. New standards will be set above what he naturally inclines to.  "New forces" or, if you like, "new strings" are involved. From that  moment on, choices are made between the old and the new, sometimes in  the form of hard-fought struggles over who is with whom.

We don't  know much about the practical life of Ishmael and Hagar beyond the above two sentences, except perhaps that Scripture later states that Ishmael grew into a nation. But one cannot help but notice a striking difference in the way life decisions are made in case of Ishmael or  Isaac. What efforts were later made to make sure that Isaac finds the right woman who was not to be from the surrounding nations. After all, it is primarily the women who determine the inner disposition of the family. Moreover, they often brought a form of godliness from their original tribe. Therefore, Abraham gave the choice of a wife for Isaac entirely to God and asked Him for a miraculous act. Scripture describes this in detail in Gen 25.

Ishmael was violent in character, and  became an archer. They lived in Paran near Egypt, so his mother gave him a woman from the area, for that was her nation. Not that these choices were in themselves a sin. However, the trajectories of Ishmael´ and Isaac´s lives and that of their descendants diverged more and more over time as other forces, other "strings" were at work. Abraham no longer wanted  to make only natural choices. He wanted to involve his God in them. He desired that Isaac would later also take up his spiritual heritage, his faith in a unique God and the path that Abraham walked in God's presence.  Therefore, he urgently dealt with God in making decisions  about Isaac's life (which, as Gen 25 shows, was quite a struggle) and did not let things run their course.

If there is anything to be learned from Abraham's life, it is in this regard.