^4-7 But when the time arrived that was set by God the Father, God sent his Son, born among us of a woman, born under the conditions of the law so that he might redeem those of us who have been kidnapped by the law. Thus we have been set free to experience our rightful heritage. You can tell for sure that you are now fully adopted as his own children because God sent the Spirit of his Son into our lives crying out, “Papa! Father!” Doesn’t that privilege of intimate conversation with God make it plain that you are not a slave, but a child? And if you are a child, you’re also an heir, with complete access to the inheritance.

^21-31 Tell me now, you who have become so enamored with the law: Have you paid close attention to that law? Abraham, remember, had two sons: one by the slave woman and one by the free woman. The son of the slave woman was born by human plotting; the son of the free woman was born by God’s promise. This illustrates the very thing we are dealing with now. The two births represent two ways of being in relationship with God. One is from Mount Sinai in Arabia. It corresponds with what is now going on in Jerusalem—a slave life, producing slaves as offspring. This is the way of Hagar. In contrast to that, there is an invisible Jerusalem, a free Jerusalem, and she is our mother—this is the way of Sarah. Remember what Isaiah wrote:

Isn’t it clear, friends, that you, like Isaac, are children of promise? In the days of Hagar and Sarah, the child who came from faithless plotting (Ishmael) harassed the child who came—empowered by the Spirit—from the faithful promise (Isaac). Isn’t it clear that the harassment you are now experiencing from the Jerusalem heretics follows that old pattern? There is a Scripture that tells us what to do: “Expel the slave mother with her son, for the slave son will not inherit with the free son.” Isn’t that conclusive? We are not children of the slave woman, but of the free woman.