The New Testament uses many images to describe what happens when someone is united to Christ. A person is justified, reconciled, redeemed, born again, sanctified. Each of these speaks a true word. But there is one image Paul is especially fond of that modern readers often glide past: adoption.
To be a Christian, Paul says, is to be adopted as a son or daughter of God. He uses the word huiothesia — literally "the placing of a son" — five times in his letters (Romans 8:15, 8:23, 9:4; Galatians 4:5; Ephesians 1:5). It is not a minor metaphor. For Paul, adoption is near the heart of what salvation actually is.
Why adoption, and not just forgiveness?
If you could only describe salvation in legal terms, you might reach for justification — the verdict that the sinner is declared righteous. This is crucial, and Paul labors over it in Romans and Galatians. But justification alone leaves a question open: once acquitted, what then? Does the defendant walk out of the courtroom as a stranger?
Adoption answers that. It says the one who was guilty is not merely declared innocent but welcomed into the household. Paul is careful to distinguish the two. In Galatians 4:4–5 he writes that Christ came "to redeem those who were under the law, so that we might receive adoption as sons." Redemption deals with the debt. Adoption deals with the distance.
"For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, 'Abba! Father!'" (Romans 8:15)
The relationship changes. Not servant to master. Not defendant to judge. Child to Father.
What Roman adoption actually meant
Modern readers imagine adoption primarily as caring for an orphan. In the first-century Roman world, the word carried a different weight. Roman adoptio was a legal act through which an adult male — often already grown, often of another family — was permanently transferred into a new household. The new father assumed full authority. The adoptee received a new name, a new line of inheritance, and a legal status that could not be revoked.
The Emperor Augustus was adopted by Julius Caesar. Tiberius was adopted by Augustus. This is how succession worked among the Roman powerful: adoption was not a consolation for the childless but a deliberate act of lineage. When Paul tells Gentile converts in Rome that they have been adopted, he is using the most public and weighty legal category available to his audience.
This is the background of Ephesians 1:5 — that God "predestined us for adoption to himself as sons through Jesus Christ, according to the purpose of his will." Paul is not offering a sentimental image. He is making a claim about status, inheritance, and permanence.
Three things adoption changes
First, your identity. Paul insists that the Spirit of the adopted child does not whisper doubts but cries out Abba — an Aramaic word Jesus himself used in Gethsemane (Mark 14:36). J. I. Packer, in Knowing God, argued that if you want a one-sentence summary of the New Testament's doctrine of salvation, it is this: Christians are those who have God as their Father. Not a distant deity. A father to whom the cry goes up in their native language.
Second, your inheritance. In Galatians 4:7, Paul writes, "So you are no longer a slave, but a son, and if a son, then an heir through God." The Christian is not simply rescued from condemnation. The Christian inherits. Romans 8:17 goes further: "heirs of God and fellow heirs with Christ." Whatever belongs to Christ by right belongs to his siblings by grace.
Third, your body. This one is surprising. Paul says in Romans 8:23 that we already have the Spirit of adoption — and yet we "wait eagerly for adoption as sons, the redemption of our bodies." Adoption is begun but not finished. The legal standing is secure; the bodily transformation is coming. The resurrection is, in Paul's mind, the last act of the adoption — the moment when the adopted child physically resembles the elder brother who has gone ahead of them.
Why this word matters pastorally
If you struggle to believe that God accepts you, the word justification may feel too courtroom-cold to comfort you. Adoption refuses that distance. It insists that acceptance is not merely a verdict; it is an embrace.
And if you are tempted to think of yourself as tolerated rather than loved — permitted into God's presence but not really welcomed — Paul will not let you. The Spirit of the adopted child, he says, cries Abba. Not "my Lord," though he is. Not "my Judge," though he is that too. My Father.
The New Testament's vocabulary is careful. It uses many words because salvation is too rich for one. But adoption may be the word that most directly answers the question a wounded heart tends to ask: Does he actually want me? Paul's answer, written to churches full of former slaves and outsiders, is yes. He chose you before the foundation of the world. He brought you home on purpose. And he does not un-adopt.
