For it is written that Abraham had two sons, one by a slave and the other by a free woman. But the one by the slave was born according to the impulse of the flesh, while the one by the free woman was born as the result of a promise…
Now you, brothers, like Isaac, are children of promise.
(Galatians 4:22-23, 28)
In the book of Galatians, Paul uses the historical narrative of Abraham, Hagar, Sarah, and their children as an illustration of God’s grace. God had promised Abraham and Sarah that they would have children, but as Sarah’s discouragement grew with her age, she encouraged Abraham to sleep with Hagar. Instead of relying on the promise of God, Abraham took matters into his own hands. His relationship with Hagar is a picture of self-reliance and self-dependence. Hagar conceived and bore a son, Ishmael, a son by the slave woman. Abraham and Hagar conceived not by trusting God, but by trusting themselves.
Still God fulfilled His promise—He always does—to Abraham and his wife. Sarah conceived and gave birth to a son, Isaac, a son by the free woman. Abraham and Sarah conceived because of God’s promise, not because of anything they had done.
Those who trust their own efforts are like Ishmael, children in slavery. They attempt to better themselves and find fulfillment in themselves. But as they do, they find themselves continually empty and enslaved.
This was a stinging passage to those who infiltrated the churches in Galatia and insisted on adherence to the law for approval before God. They boasted of their Jewish heritage and lineage, boasted that they descended from Abraham and Isaac. And Paul is saying, “If you return to the Law for your standing—you are actually in the lineage of Hagar and Ishmael. You are really a slave.”
But we, “brothers, like Isaac, are children of promise.” We are Christians not because of anything we have done, not because of our impulse, our desire, our efforts, or our merits. We are Christians only because of His grace. We have been supernaturally born of God.
We can rest in the reality that we are His. If our salvation depended on us, we would certainly lose it. Our salvation, our standing before God, is based on His perfection, His promise, not ours. We are secure because of Him and His work for us. His promise trumps our sin, our shame, and our wandering.
We live as either Isaac or Ishmael. John Stott writes:
The Ishmaels of this world trust in themselves that they are righteous; the Isaacs trust only in God through Jesus Christ. The Ishmaels are in bondage, because this is what self-reliance always leads to; the Isaacs enjoy freedom, because it is through faith in Christ that men are set free.
Our standing before God is based on His promise, not ours.