Isaac was Abraham’s promised son. The covenant God made with his father continued through him. The Bible gives relatively little information about Isaac. He is especially contrasted with his half-brother Ishmael.
The promised “offspring”
When the LORD promised Abraham to give him many descendants, there was an obvious problem: his wife Sarah was not able to have children and, by that time, she was also much too old. First, Abraham thought that he should accomplish this by adopting his servant Eliezer. But God said, no; it will be your very own son (Gen 15:3-4).
Next, Abraham and Sarah concluded that they should use a younger woman as a surrogate, to carry the child instead of Sarah. (It was not uncommon at that time to obtain an heir in this manner.) So Hagar, Sarah’s young servant, gave birth to Abraham’s first son, Ishmael. “Oh, that Ishmael might live before you!” Abraham prayed (17:18). But the LORD insisted: the covenant promises will be realized only though a son of both Abraham and Sarah. There will be no legal or biological surrogates.
And so Isaac is born. This is a miracle of the highest order. It is fair to say that here the LORD created an entire nation that should not, could not have existed in the first place. Sarah conceives a child at age ninety, an absolute medical impossibility. (See also 18:11)
Isaac is the first in a line of miraculous births, from women that are either too old, infertile, or a virgin. Further examples in the Bible are
- Jacob and Esau from Rebekah (Gen 25:21);
- Joseph and Benjamin from Rachel (Gen 31:22);
- Samuel from Hannah (1 Sam 1:19);
- John from Elizabeth (Luke 1:24);
- Jesus from Mary (Mat. 1:18).
If there is one lesson to learn here, it is that God takes a delight in the supernatural creation of nations and saviors. Not the evolution of humankind and its culture, but the miraculous power of the LORD brings about salvation!
Isaac, Ishmael, and the covenant
The situation in Abraham’s household became complicated. Thirteen-year old Ishmael was understandably jealous of his baby brother, the legal heir. Ishmael had been circumcised as a sign of covenant membership; but he was not the son of the covenant promise. The LORD declared:
As for Ishmael, … I have blessed him and will make him fruitful and multiply him greatly. He shall father twelve princes, and I will make him into a great nation. But I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year. (Gen. 17:20-21)
While the LORD had made the covenant with Abraham and his offspring, the covenant “line” with its promises continued through a narrower channel. Ishmael received some of its blessing, but the covenant itself did not extend to his family. It is God’s prerogative to determine the way in which the covenant promise will work out. Again, it is not the natural, biological development of mankind but God’s gracious initiative that determines the history of salvation. In the New Testament, Paul underscores this:
Not all who are descended from Israel belong to Israel, and not all are children of Abraham because they are his offspring, but “Through Isaac shall your offspring be named.” This means that it is not the children of the flesh who are children of God, but the children of the promise are counted as offspring. (Rom. 9:6-8)
God’s way with his people involved a generation pattern, from father to son, but it was never automatic and never general. Ultimately, as I noted in before, the covenant line narrows to one person: Jesus Christ, from the family of Abraham, Isaac, and so on. He is the ultimate “offspring”.
Ishmael is sent into the desert, with his mother Hagar. This was done for the very practical purpose of resolving the unbearable tension in Abraham’s household. (Polygamous households tend to invite that kind of trouble.) But it is also an important symbolic action: Ishmael must leave the covenant community, just as in the past Cain was sent to Nod, the land of “wandering”. The episode in Gen 21:8-21 shows that God did not forget to protect and bless Ishmael; but his descendants would be perpetual desert dwellers (they are today’s Arabs), at home in a land of death and drought.
Meanwhile, Isaac grows up as the son of the promise. In a way, he inherits the covenant, as from the beginning of his life he belongs to it and experiences its blessing. At the same time, God’s relationship with Isaac did not remain indirect. The LORD also appeared to Isaac personally, and gave him the same promises his father had received (Gen 26:3-5).
The Binding of Isaac
The most beloved story involving Isaac is that of Genesis 22, known to the Jews as Aqedat Yitzhaq, “the Binding of Isaac”. It begins with a most shocking instruction from the LORD: Abraham must bring Isaac to a mountain top and offer him there as a sacrifice to God. The story is told in practical detail; this was not a symbolic action but a real sacrifice, in which Isaac was to die a bloody death, like a sacrificial animal. Abraham faced the terrible choice between disobeying God and killing the miracle son he had received, who was his only heir and the only hope for the covenant promises.
Abraham complied with the LORD, a three-day long act of the most profound faith. The New Testament comments:
By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises was about to offer up his only son … He considered that God was able even to raise him from the dead, from which, figuratively speaking, he did receive him back. (Heb. 11:17-19)
Not before Abraham has bound Isaac and raised his knife to perform the sacrifice, the LORD stops him. God himself miraculously provides an animal—a ram—to be sacrificed instead.
This story is of the greatest importance in the Bible. It shows, first of all, God’s right to claim what is really his; in the Law of Moses, every firstborn son is declared to belong to the LORD (e.g. Ex 22:29). Second, it shows that animal sacrifices would be accepted as a substitute; throughout the Old Testament period, worshipers slaughtered animals to be given to the LORD in their place. Third, the ram shows that God himself graciously provides the means of redemption. This is highlighted in Gen. 22, when the mountain is called “Moria”, “Provision”. It was a geographical monument to the God Who Provides. Fourth, Christians have always viewed the Binding of Isaac as an anticipation on the work of Jesus, who was sacrificed on the altar of the cross; at the same time, he is the ultimate “ram”, substituted in the place of each of us, sinners.