We know that the man Abraham, first named Abram, fathered quite a number of sons during his life. In fact, over ten of them are named in the Bible. There can be no doubt from the biblical record that Ishmael, for example, was born quite some time before Isaac. However, when God spoke to Abraham regarding the sacrifice of Isaac, He referred to him as Abraham’s only son. How odd.
If one were a first son, then one could possibly be an only son. However, given the fact that Ishmael was born to Abram some fourteen or fifteen years before Isaac was born makes Isaac neither “first” nor “only” in the category of sons of the patriarch. Most of us don’t believe that God is either a liar or a fool. But, in chapter 22 of Genesis, God spoke to Abraham and required him to go to a certain place and there sacrifice his “only son.” So, let’s get that straightened out if we can.
On a certain night about a year before the birth of Isaac, God had come to the man named Abram and had given him very explicit instructions concerning a particular covenant. He – God – was formalizing a covenant of a very particular and unique nature that night. That covenant involved the future of Abram and his progeny essentially into a “forever” future. Years earlier God had promised to make Abram into a “great nation.” Now that promise was being fully formalized. Along with that formalization, God was requiring some things of Abram. First, his name was to be changed. He was not to be called Abram any longer. His new name was to be Abraham, and that was the name by which he was always called thereafter. His wife’s name was to be changed as well.
In order to memorialize the covenant and the new names, Abraham was given instruction to take on a permanent reminder. He was to circumcise himself. That was a rather permanent thing. Once he had circumcised himself, he would not un-circumcise himself. Whatever the purpose of the circumcision, it should be a permanent purpose to warrant the mark that was to be made in Abraham’s flesh. The covenant was to be permanent, so the mark was matched in its permanency. From that day, the shepherd who had been named Abram would no longer be named or called Abram; he would be named and called Abraham. His identity was changed from that point. He would no longer be uncircumcised; he was to be permanently circumcised. His wife would no longer be named or called Sarai; she would be named and called Sarah. Things were forever different for this couple, and therefore for the people who depended on them. They were not the same people anymore, and Abraham bore that new identity in his very flesh.
But, there was another part to this whole thing. On the same night when God gave Abram these instructions, He also told him that Abraham would have a son and that son would come forth from the womb of his barren wife. Her name had been Sarai, but she was to be called Sarah from now on. He told the new Abraham that He would see to the birth of his son in about a year. Not too many months, then, after the two had their names changed by God, a pregnancy would occur. She who had been barren for almost ninety years would become pregnant and have a son for her husband. God was speaking it before it could happen.
After a few months, Sarah was found to be with child. The barren womb now had a child growing in it. That child was the child of Abraham. Sarai was not impregnated, Sarah was. Abram had not brought about the pregnancy, Abraham had. We may say that the man Abraham had not had a son before – only Abram had done so. The biblical record makes it plain that the woman Sarai had never been pregnant. In the new pregnancy it was the woman Sarah who was the one who was to have a son. Clearly, this son was to be the “only son” of Sarah. To argue that he was the only son of Abraham, though, is to argue that Abraham was not the same person as Abram. How about that!
The name change was not all that mattered. Anyone could change a name when they wanted to. No, the real change was the mark in the flesh of the man. The covenant was in the air, and because of it God had required that Abraham circumcise himself to permanently memorialize its future impact in the world. So this fellow had a new name, and he was a new man in his circumcision.
That change is important to us. The covenant was announced, and then the circumcision was performed. Then, in a few months, the improbable impregnation occurred. Abraham’s wife, Sarah, would have the son of the man who was the recipient of the covenant of God that involved the nation of God’s choosing, the “holy” nation.
Only this particular combination of man and woman could qualify to parent this child. No other womb could bear this child, and no man who was not circumcised could be his father. Isaac was the first man to be born under the covenant, and it was necessary that he be born to one circumcised because circumcision was the mark of the context of the covenant. This, then, was the only son of this particular pair.