Like Justification, adoption is a legal term. How we think about adoption today differs from how the word was used in the New Testament era. The Jew had no idea of adoption. For them, they considered everyone as the child of Abraham, children of the covenant, hence the Children of the most high God (Deuteronomy 14:1; Jeremiah 3:19). But as we come into the New Testament, the idea of adoption becomes rampant since the Romans brought it. According to the Romans, they adopted it based on need. You would find a wealthy older man who cannot take care of himself and his estate; he would go on to adopt a son who is intelligent enough to care for him and eventually inherit the estate. Paul is using adoption to explain to us the relationship we have with God as children, that we are by right (legally) God’s children when we believe in Jesus Christ (Galatians 3:29). God takes us in who were otherwise desolate and fatherless to be his children (John 1:12).
The Privileges of Adoption
Adoption, of any kind, comes with its privileges and responsibilities. In Romans 8:12-29, Paul highlights the privileges of adoption. John mentions the reason for our adoption as saints is the great love of God. In the way of worship, he said, “Behold the manner of love the Father has lavished on us that we should be called the children of God. Yes, we are!” 1 John 3:1. This marks the first privilege of adoption. All who are adopted in Christ by God enjoy the love of God (Romans 5:5). This means that it wasn’t anything about us that made God choose us, only his grace and mercy.
As adopted children of God, we are brothers and sisters in the Lord (Romans 8:12). It is pretty encouraging to meet people you’ve never met before, and when you find out that you’re all in Christ, there comes this deep, genuine bond you feel because we have one Father and God, our Lord Jesus. Not only are we brothers but also the sons of God (Romans 8: 14;19). Our sonship to God is further affirmed by the Spirit of adoption (Romans 8:15), and if sons, then heirs together with Christ (Romans 9:17). What an incredible privilege for the children of God (Romans 8:16;21). The last privilege comes through having Christ as our brother (Romans 8:23). Since we are coheirs with Christ, our brother, then God can withhold nothing from us (Romans 8:32).
The other privilege is that God gives us an inheritance through our sufferings (Romans 8:17-35). In Romans 5, Paul taught that tribulations lead us to hope in glory. Here, he is saying that the suffering of this world is nothing compared to the glory that is to come. “The relationship between suffering and the glory of a believer is not merely chronological but causal,” writes Sinclair Ferguson. This might partly imply that suffering is the means by which we receive eternal glory.
The Spirit of Sonship helps us in our weakness (Romans 8: 26-27). This means that, left alone, we cannot pray properly. We cannot lift our requests to God as we should. So we have the privilege of the Holy Spirit, who helps us to lift our prayers to God. How does the spirit help? By interceding for us according to the will of God. The Holy Spirit comes down to us and raises our weakness to God with groanings too deep for words.
Lastly is the privilege of placing our confidence in God’s sovereignty (Romans 8:28). We know everything works for the good of those who love God. The good of the believer is that we will be transformed into the likeness of our Lord Jesus (Romans 8:29).
The Responsibilities of Adoption
We are not just guilty sinners who have been justified; we are also privileged prodigals. “The privilege of adoption is the apex of redemptive grace,” said John Murray. J.I. Packer also commented, “If you want to know if someone knows what it means to be a Christian, ask him how much he knows God as Father.” Understanding that we are adopted children of God changes how we view life altogether. This is because no ordinary believer has the privilege by his experience to come to God as Father unless God brings them. Take, for instance, an adopted child; the only way of them knowing their adoptive parents is by spending time with them. In our case, we are responsible for knowing God, and we know him by interacting with the Scripture.
Secondly, those who walk by the Spirit of God put to death the things of the flesh (Colossians 3:5-11). By putting the flesh to death, we experience what it means to be a child of God. They now exhibit the likeness of Christ Jesus and become more like him (Romans 8:29). The Spirit of God is helping us produce the character expected of all believers worldwide. Sharing these traits in hating sin and loving godliness is a privilege. If people are raised in the same household, they may have similar mannerisms, and so is it for Christians in the household of God.
We certainly have the privilege of a deep-seated assurance that we are the children of God (vs. 13-16). Evidence of this assurance by calling God Abba father, the Holy Spirit bears witness that I am a child of God. Here, we have two witnesses in us establishing the testimony that God is our Father; these witnesses are the Spirit of God and your spirit deep down calling out to God, Abba Father! This is a loud cry of desperation, the same cry that Christ called when he was on the cross. This instinct to call God Father in this way, in despair or doubt, is the most basic thing about any believer. We all have it, thanks to the Spirit of adoption. We have the privilege of having the Holy Spirit—the Spirit of sonship, the Spirit of adoption.