It is not the children of the flesh who are the children of God, but the children of the promise are counted as offspring. (Romans 9:8)
Picture the Old Testament Abraham as a pastor. The Lord says, “I will bless you and prosper your ministry.” But the church is barren and bears no children.
What does Abraham do? He begins to despair of supernatural intervention. He is getting old. His wife remains barren. So he decides to bring about God’s promised son without supernatural intervention. He has sex with Hagar his wife’s handmaid (Genesis 16:4). However, the result is not a “child of the promise,” but a “child of the flesh,” Ishmael.
God stuns Abraham by saying, “I will give you a son by her [your wife Sarah]” (Genesis 17:16). So Abraham cries out to God, “Oh that Ishmael might live before you!” (Genesis 17:18). He wants the work of his own natural, human effort to be the fulfillment of God’s promise. But God says, “No, but Sarah your wife shall bear you a son” (Genesis 17:19).
But Sarah is 90 years old. She has been barren all her life, and she has already passed through menopause (Genesis 18:11). Abraham is 100. The only hope for a child of promise is stunning, supernatural intervention.
That is what it means to be a “child of the promise” — to be born “not of blood nor of the will of the flesh nor of the will of man, but of God” (John 1:13). The only children that count for children of God in this world are supernaturally begotten children of promise. In Galatians 4:28 Paul says, “You [Christians], like Isaac, are children of promise.” You are “born according to the Spirit,” not according to the flesh (Galatians 4:29).
Think of Abraham as a pastor again. His church is not growing the way he believes God promised. He is weary of waiting for supernatural intervention. He turns to the “Hagar” of mere human devices, and decides he can “attract people” without the supernatural work of the Holy Spirit.
However, it will not be a church of Isaacs, but Ishmaelites — children of the flesh, not children of God. God save us from this kind of fatal success. By all means work. But always look to the Lord for the decisive, supernatural work. “The horse is made ready for the day of battle, but the victory belongs to the Lord” (Proverbs 21:31).