As Isaac grew older the complicated structure of his family started to become a reality in his world: he realized that his old parents, as kind and loving as they were, could not play with him at all. It is at this point that he probably turned his attention to that really cool brother of his (he didn’t know and didn’t care about the difference between a brother and a half-brother) who was the only youth in the family. Ishmael was always ready to play with him, was an amazing archer and might have promised to teach him to shoot a bow as soon as he was tall enough to hold one.
In my opinion, not only did Isaac love Ishmael, he absolutely admired his big brother (as most younger brothers do). I think it was precisely Isaac’s great love for his brother and Ishmael’s huge influence on Isaac that became the main reason for Sarah’s (and God’s) concern. Think of it: If the reason for Sarah’s reaction in our famous scene had been Ishmael’s bad attitude toward his younger brother, this clash would have happened much earlier, when Isaac was still a helpless baby. Ishmael could have expressed his bad attitude on many occasions before that one. However, the story happened only after Isaac became a toddler, after his relationship with Ishmael became mutual and Sarah could see with her own eyes what a huge love her son held for Ishmael and what a huge problem Ishmael’s influence presented.
What Did Sarah See?
And Sarah saw the son of Hagar the Egyptian … scoffing
And now we come again to that dramatic scene—to the “family dynamics” of Genesis 21. Isaac is about two or three years old and he has just been weaned. A big party is thrown on this occasion. Probably during the party, or around this time, Sarah sees Ishmael, now a teenager 16 or 17 years old, metzahek–“laughing” or “playing” or “scoffing”. She is infuriated and says “to Abraham: Cast out this bondwoman and her son; for the son of this bondwoman shall not be heir with my son, namely Isaac.” Why? What did Sarah see?
The Hebrew word metzahek has different meanings, and no one knows exactly what it means here. Some commentaries suggest a sexual connotation. After all, this is the same word that we find in Genesis 26, where it refers to Isaac and Rebecca, undoubtedly with a sexual meaning: Isaac was sporting (metzahek) with Rebecca his wife. Does it have the same meaning here? Was Ishmael sexually molesting Isaac? And was it because of this sexual abuse that Sarah was so infuriated? In Genesis 26 it is quite clear, Isaac metzahek with Rebecca; while in our case, based on the text itself, it isn’t even clear that Ishmael was interacting with Isaac at all when Sarah saw him—Isaac is not even mentioned in this sentence. So, what did Sarah see and why was her reaction so turbulent? And even more important: why did God support Sarah?
Why Did God Support Sarah?
Why did God support Sarah? Why did God completely back up what seemed to be a very exaggerated reaction of an infuriated and jealous mother? Sarah could have made a mistake; we have seen her make huge mistakes before. So, I wouldn’t be surprised if the whole situation could be explained away solely as an exaggerated reaction of Sarah’s: it’s almost scary to discover how easily and quickly we lose our inner peace when our children are involved. I imagine that if Abraham had thought this terrible request was only an overreaction of Sarah’s, he wouldn’t have been quite as disturbed. However, to Abraham’s great surprise and displeasure, God completely supported Sarah in this request. Why?
Let us turn to Hebrew for the answer. If you know Hebrew letters, you will recognize that the word metzahek, מצחק, has the same root as Itzhak: יצחק. Therefore, it can be read as a verb formed from the root, “Isaac”. Sarah saw that Ishmael was “Isaacing” – whatever that might mean! Ishmael was probably trying to take Isaac’s place – maybe in Abraham’s family, maybe in God’s plan, maybe in both! In my opinion, this unexpected, and only-in-Hebrew visible explanation, can account, not only for Sarah’s stormy reaction, but also for God’s command to banish Ishmael from Abraham’s camp!
Regardless of what Sarah saw, Ishmael was a natural, man-made son. He had been conceived and born naturally—unlike Isaac, who was the child of a miracle, conceived and born in a totally supernatural way. Ishmael was “Isaacing”, trying to take Isaac’s place – and had the boys continued to live together, nothing would have come of God’s plan to make His own peculiar people from Abraham’s family. God wanted to separate the son who was born, not of blood, nor of the will of the flesh, nor of the will of man, but of God, from the son who was born in a natural way and was destined to be part of the natural world. Isaac was supposed to belong to Him completely. The first commandment says: I AM THE LORD YOUR GOD… you shall have no other gods before Me. In Abraham’s case, the Lord personally sees to it that his family and his son will keep this commandment.
Thus, we are beginning to understand that for Isaac to grow up in God’s covenant and as a testimony to God, he had to be separated from Ishmael’s influence, and that is why the boys had to be separated. This is why Ishmael had to be sent away, and somehow Sarah, with her love for God, understood this. It always amazes me to see that God still carries out His will and His plan through people’s mistakes and emotional reactions. I suppose most of my readers know the story of Joseph and his brothers at the end of the book of Genesis. In that story, through all the bad things that the brothers did to Joseph, God still implemented His plan—for Joseph and for Israel. It’s the same here: As emotionally involved as Sarah was in this story, it still seems that she wasn’t acting out of her anger alone, but out of her prophetic gift as well (as happens a few chapters later in Esau’s and Jacob’s story, where it was Rebecca, not Isaac, who saw God’s plan and God’s heart). Although her reaction was very emotional and evidently exaggerated, separating Isaac from Ishmael and leading them both to completely different destinies was God’s plan in the first place!
 Gen. 21:9
 Gen. 26:8
 John 1:13
 Exodus 20:2-3