We become God’s sons and daughters in Christ via adoption, and this truth helps us maintain a proper understanding of humanity and the depth of God’s grace. Most people, at least in Western society, would affirm that we are all children of God. If this were true, however, there would be no reason why anyone would need to be saved. After all, what would be the point of Jesus’ ministry if we are all a part of God’s family and the recipients of His love? But the assumption that we are all children of the Lord fails to reflect biblical teaching, for the Bible does not teach that all people are God’s children. In fact, in our fallen condition apart from Christ, we are all children of the devil (John 8:39-47; Rom. 5:12-21). Due to our depravity, the only way we can become children is through adoption. Since the fall, we are not by nature a part of God’s family. Atonement must be offered and our disposition—inclined as it is toward sin because we sinned in Adam—must be changed. The extent of depravity is seen in that we are not inherently the children that the Lord made us to be (initially, Adam was God’s “son”; Luke 3:38). The depth of God’s grace is evident in that our Father nevertheless adopts believers as His children in Christ (John 1:12-13). Our adoption is not merely a legal declaration; it also establishes the deepest of relationships. We are privileged to call God “Abba” (Rom. 8:15). The word Abba, taken from the Aramaic language that Jesus and other residents of first-century Palestine spoke, was the most intimate term people could use in addressing their fathers. That we can use it for God indicates that the Lord enters into the closest familial relationship possible with His people. God the Holy Spirit bears witness with our spirits that we belong to Him as His children (v. 16). There is an internal testimony within the hearts of believers that assures them of God’s fatherhood and preservation of them as His beloved sons and daughters. Note that the Spirit does not give testimony apart from His Word. Paul has to tell us that we are children of God, just as the Lord has always given an objective Word to His people through the prophets. The Spirit takes this external Word and confirms it internally. He provides subjective assurance that God’s objective Word applies to us when we believe. Because we are children, we are also heirs (v. 17). Paul alludes here to the grand promises to Abraham of land and blessing (Gen. 12:1-3). In Christ, we have an inheritance awaiting us. The world is ours by legal right, and one day we will possess it in its fullness.