Adoption as Sons: The Purpose of the Incarnation
Sermon Series: Advent 2025
Message By Eddie DSouza on December 21, 2025
Passage: Galatians 4:1-7
J.I. Packer calls adoption “the highest privilege that the gospel offers: higher even than justification… because of the richer relationship with God that it involves.”[1] As you have just heard, Scripture teaches that the purpose of the incarnation is that we might receive adoption as sons (Gal 4:5). This is the highest privilege that the gospel offers. Today, we will attempt to study this great privilege with a twofold hope. First, I hope that this doctrine will produce in you much godward gratitude. Second, I hope this sermon will stir you to obedience that flows from the consequences of this doctrine. To that end, let me pray.
Heavenly Father, we come to you this morning to consider your great act in the adoption of sons. By your Spirit, would you help us to understand this doctrine as well as to respond in gratitude and obedience. Amen.
This sermon has two stages. In the first stage, I will explain the doctrine of adoption. In the second stage, I will teach you what the doctrine requires. Two simple parts—explanation and application; the doctrine of adoption and the demands of adoption.
The Doctrine of Adoption
In the English language, adoption is the act of making someone who is not your biological child your own child. The word has Latin roots. Ad + optare, which means “to choose” (think of the words: option, to opt, optative). The act of selecting an individual to be considered as one’s own child is generally understood as adoption.
In the Kannada language, “ದತ್ತು ಪುತ್ರ” is the word for adopted son. Dattu (ದತ್ತು) – This word is derived from the Sanskrit root verb dā (दा), meaning “to give” or “to grant.” The form “dattu” means “given” or “granted” (in the sense of a child given up for adoption by biological parents or granted by law to adoptive parents).
In the New Testament, the word adoption, as found in most modern English translations, occurs only in the Pauline letters. Adoption is the English translation of the Greek υἱοθεσία. This noun is formed by combining the noun υιος (meaning son) and the verb τιθημι (meaning to put or to place), giving us the meaning “to place as son” or “to appoint as son.” Adoption carries the meaning we commonly associate with it—to make someone one’s son who was not one’s son. Adoption is the act by which God grants the Christian the right to be called his child.
There are many aspects of salvation. You may have read in the Bible words like election, predestination, justification, adoption, sanctification, and glorification. All these words are aspects of salvation. Some of them are acts, others are works. An act is something that God does by a declaration. He declares a person justified. He declares a person as adopted. He works sanctification in a person. Glorification is a work of God where a natural person is raised to a spiritual person.
We will examine all the passages in the Bible that teach about adoption and develop a definition of adoption. The word adoption appears five times in the New Testament (Rom 8:15, 23; 9:4; Gal 4:5; Eph 1:5). We will begin by looking at Ephesians, then return to Galatians, and finally examine Romans.
Adoption in Ephesians
Ephesians 1:3–14 is one long sentence in the Greek language. In this passage, we learn that God and Father of our Lord Jesus Christ chose us in Christ before the foundation of the world that we should be holy and blameless before him (v. 4). This act of choosing is called electing. Based on his electing love and according to the purpose of his will, he predestines us for adoption to himself as sons through Jesus Christ (v. 5). Based on what we have seen so far, we can reasonably conclude that adoption is an act of God’s free grace flowing from the electing love of God and Father in eternity.
If we look at the following few verses (vv. 7–10), Paul describes the redemption we receive through Jesus—the forgiveness of sins, and the uniting of all things. Then, in vv. 11–14, Paul says that Christians have obtained an inheritance in Christ. “In Christ” is an important phrase that describes a reality that we call union with Christ. Those who hope in Christ, that is, believe him for the forgiveness of sins and reconciliation with God, are united with Christ. When they believe in Jesus, that is, when they place their faith in Jesus or at the moment of their union with Christ, they are sealed with the Holy Spirit, who guarantees their inheritance until they acquire possession of it. Thus, they are heirs now, but their inheritance is yet to be possessed. Let us add these findings to our definition. Adoption takes place by faith at the moment of union with Christ. It is an act of God’s free grace flowing from the electing love of God and Father in eternity. It immediately confers the privilege of being one of God’s heirs.
Adoption in Galatians
Gal 4:1–2 provides us with an illustration by which we can compare what it means to be adopted as God’s sons. In the Greco-Roman world, a child had the same status as a slave until he was appointed as son by his father. Even though this child was going to inherit everything, he was not yet the owner of anything. During this time, he was under guardians and managers—people who would educate him and prepare him to take over his inheritance. There are three concepts to keep in mind with this illustration. First, there is the child who is not yet the son but has the status of a slave. Second, there are the guardians and managers. Third, there is an appointed time. Paul explains that at the appointed time, the fullness of time, God sent forth his Son, born of a woman. Friends, that is the incarnation. Our guardians and managers were the elementary principles of this world. Based on vv. 9–10, the elementary principles of this world appear to be the cultic calendar, referring to the festivals and ceremonies of the Mosaic law. Finally, our status before our union with Christ is that of a child, a slave.
The purpose of the incarnation is that we might receive the adoption as sons. Look at v. 5. To redeem those under the law—the immediate purpose; so that we might receive the adoption of sons—the ultimate purpose. Adoption is the highest privilege of the gospel; higher than justification.
At this point, some parts have gotten tricky. It was there in Ephesians, too. But more so in Galatians. First, it appears that adoption took place when the incarnation happened because you were children until the fullness of time had come. Second, it appears that adoption is yet to take place because it does not say we have received the adoption as sons, but that we might receive the adoption as sons. Third, v. 6 says, “Because you are sons, God has sent the Spirit of his Son into your hearts.” This suggests that adoption has taken place at your conversion or union with Christ. Which one is it? Let us examine Romans before we conclude anything further at this point.
Adoption in Romans
Rom 8:15–17 teaches us that we are the children of God because we have received the Spirit of adoption. Nevertheless, Rom 8:19–25 says that all creation and we, Christians, eagerly await the adoption as sons, the redemption of our bodies. The adoption as sons is completed at the resurrection of our bodies. So, on the one hand, it has been inaugurated when we were united with Christ; on the other hand, it will be concluded at the resurrection of our bodies. Thus, adoption as sons is an act of God connected to all three: election in eternity past, regeneration in time, and resurrection in the future. Adoption is also very trinitarian. The Father, Son, and Holy Spirit are involved in our adoption as sons.
Based on what we have seen in the Bible, we can define adoption as follows. “Adoption is a change in legal status from that of slave to that of son of God, which takes place by faith at the moment of union with Christ, but will be publicly revealed at the resurrection. It is an act of God’s free grace flowing from the electing love of God and Father in eternity and the regenerating power of the Holy Spirit in time, and immediately confers the Spirit of adoption and the privilege of being one of God’s heirs.”[2]
This is the doctrine of adoption in a nutshell. It is the highest privilege of the gospel. It is the ultimate goal of redemption. It is what we hope for. But it also has some obligations. Adoption makes some demands on us.
The Demands of Adoption
We will consider the demands of adoption from Ephesians, Galatians, and Romans in that order.
Demand from Ephesians
After the long sentence in Eph 1:3–14, Paul prays for the Ephesians. One of his prayer points is that they may know what the hope to which God has called them (v. 18). He explains that hope as the riches of his glorious inheritance in the saints. An incredible bounty awaits Christians. God’s power, his power in raising Jesus from the dead, is available to every Christian to help the Christian get to that glorious day to inherit this bounty (v. 19). God does that by making us spiritually alive (Eph 2:4–6). The reason for making us alive is mentioned in v. 7. There it is again. God is going to show his grace, the immeasurable riches of his grace—his great favor toward us. The reason that everything in heaven is grace is that it is not a result of works (vv. 8–9). Paul’s point is that no one can boast in heaven.
At this point, you must ask why Paul is connecting God’s favor (his grace, his glorious inheritance) to works? What can a Christian boast about in heaven (assuming he can boast)? Look at v. 10. A Christian is God’s workmanship. God is working in the Christian to enable the Christian to walk in good works that God prepared for him beforehand. The good works are rewarded with heavenly bounty. Thus, in an absurd sense, a Christian who has a greater reward in heaven could say, “I have earned this with my hard work.” But Paul says that all the good works that a Christian has done are prepared by God beforehand and worked out by God in and through the Christian. Therefore, the Christian cannot boast. Moreover, in heaven, we will be so sanctified that we will be completely content with what we have, and we will genuinely rejoice with those who have more than us.
Some of you may be saying to yourselves, “But what has this got to do with adoption?” Your adoption has begun and will be completed when you are raised and receive your inheritance. There are two implications. First, since your inheritance is tied to your good works in some way, shape, or form, you should want to glorify God as much as you can by doing those good works. Second, as a son of God, you should be about your Father’s business. Since he has prepared good works for you to do, you glorify him by doing those works.
Demand from Galatians
Some false teachers plagued the Galatian church. The false teachers taught them that to be a Christian, they ought to follow the Mosaic law. Paul clarifies that they are Christians and sons of God. The evidence of their relation to God is not in keeping the law but in receiving the Holy Spirit. So, he urged the Galatians not to return to the elementary principles of the cultic calendar and practices, but to be filled by the Spirit. In other words, since you are God’s sons, behave like God’s sons.
Demand from Romans
In Rom 8, Paul teaches that nothing can keep the children of God from God’s love for them. He exhorts the Romans to serve God boldly, without the fear of dungeons, demons, or death. Just look at the last few verses of the chapter. Nothing can separate a Christian from God’s love. How can Paul make such a claim? Can sin not separate a Christian? Can the devil’s trickery not threaten a Christian’s security and assurance in Christ?
Paul assures us with this most beautiful and incredible truth. Look at Rom 8:32. He who did not spare his own Son but gave him up for us all, how will he not also graciously give us all things? What is the logic of that statement? God owns all things. God’s dearest possession, his heart, is not in the things of heaven but his own Son. Jesus is most dear to God. If God gave up Jesus for us, then he is willing to give anything else. The logic of this verse is not in our intrinsic value but in God’s love for us. If God so loved us and gave his Son for us, he will give us anything. Nothing can separate us from such love. Because of this love, Paul can say that those whom God predestined, he justified, sanctified, and glorified.
As glorious as the gospel is, what is the demand? Look at vv. 16–18. The fact that we are children of God means we are heirs and will receive our inheritance. However, there is a proviso—a condition that we must satisfy. Look at v. 17. “… provided we suffer with Christ in order that we may also be glorified with Christ.” Our adoption demands that as sons of God we follow in the footsteps of the Son of God. We must be willing to suffer for the cause of the gospel. Look at v. 18. The present suffering is nothing compared to the future glory that will be revealed. Heb 12:2 tells us that Jesus endured the cross for the joy that was set before him. We, too, are exhorted to suffer for the joy and glory that is promised to us.
Brothers and sisters, the Bible says, “He will render to each one according to his works: to those who by patience in well-doing seek glory and honor and immortality, he will give eternal life” (Rom 2:7). Do you seek glory? Do not fear suffering. Do you seek honor? Do not fear man. Do you seek immortality? Do not love the world.
Jesus came into the world to adopt you as a son of God. If you are not a son of God, this is an invitation to you to be united to Christ. If you are a son of God, this is a reminder to behave like one.
[1] Knowing God, 3rd ed. (1973; London: Hodder & Stoughton, 2005), 232–33.
[2] Samuel E. Waldron, A Modern Exposition of the 1689 Baptist Confession of Faith, 3rd ed. (1999; New York: Evangelical Press, 2005), 170.