Martin Luther, whose tormented conscience and anguished thinking launched the Protestant Reformation, once remarked, “If the doctrine of justification is lost, the whole of Christian doctrine is lost.” It is hardly surprising, then, that there is voluminous Protestant literature on justification.

The doctrine of adoption, by contrast, has been largely neglected. Yet the two are inseparably linked.

Grace Beyond and Above

Which is not to say that they are identical. Adoption is a grace beyond and above justification. In justification, God acquits sinners of all the charges against them. Indeed, he goes further still and declares that in Christ their righteousness meets the highest possible standards. They are as righteous as Christ himself (2 Corinthians 5:21). There is not a stain on their characters.

At this point, in normal human systems of justice, the accused is then simply free to go, and both he and the judge hope they will never see each other again. But the divine judge not only acquits. He invites the sinner home — and not just for an evening. He adopts us as his own forever, tells us we are to call him “Father,” and pronounces us lawful heirs to all he is and to all that he has.

Paul is the only New Testament writer who uses the term adoption, but he is not the only one who speaks of believers being God’s children. John also highlights it, particularly in 1 John 3:1. “See,” he exclaims, “what kind of love the Father has given to us, that we should be called children of God; and so we are.” Yet while they speak of the same subject, the two apostles use different language, and to get anything like the full doctrine we need to look carefully at each.

Change in Status

The word adoption, like the word justification, refers not to a change in our disposition and character, but to a change on our status. It speaks of a revolution in our relationship with God. As unbelieving sinners, we were utterly alienated from him: total outsiders, as far as his family was concerned. Now we belong, and by using the term adoption, Paul is using formal legal language to remind us that our membership of our new family is absolutely secure. It can never be undone.

There is a parallel to all this in the story of Moses. The abandoned Hebrew baby, born as a slave under sentence of death, is taken into the palace by a royal princess, and formally adopted as her son. It is just so with believers in relation to God. He is committed to us. He has given us his name. He has made us his heirs, and solemnly pledged that as our heavenly Father, he will provide for us with the lavishness that befits his means as possessor of all the riches of glory (Philippians 4:19).

He has said, in effect, “From now on, you have nothing to worry about (Matthew 6:26). I will care for you (1 Peter 5:7), and if you do ever find yourself overtaken by anxiety, come and talk about it to me at once (Philippians 4:6–7). Always remember that I am your home, and that I will never disown you; and should you ever go astray, I will always take you back (Luke 15:20). My love will never let you go.”

Transformation in Heart

But adoption as a human transaction leaves the heart unchanged, and this is why the language of John is such an important complement to the language of Paul. Where Paul speaks of “adoption,” John speaks of being “born again”; and where Paul emphasises our being God’s “heirs,” John speaks of our being his “children.”

Adoption, whether in the ancient world or the modern, gave rights, but it did not transform; but when we are “born of God,” his “seed” (sperma) is in us (1 John 3:9). This is why Peter can even go so far as to say that we become partakers of the divine nature (2 Peter 1:4), while Paul declares that at the heart of God’s purpose for the universe lies his determination that one day every one of his adopted sons and daughters will be as glorious as his only begotten Son (Romans 8:28–29).

For the time being, sadly, this is not how we appear: To deny that we are sinners is to deceive ourselves (1 John 1:8). But by the time Christ returns, our likeness to our Father will be unmistakeable (1 John 3:2), and he will have no hesitation about making us stand in the full light of his glory (Jude 24). We will be his pride and joy.

A New People

Divine adoption, then, secures what no human adoption can secure. It is always accompanied by a radical and total transformation at the very core of our being. Not only have we a new status. We are new people (Ephesians 4:24).

Should we, then, just sit back passively and let grace do its work? Not for a moment! Indeed, the seed that God has implanted in us won’t let us sit back, nor will the hope that God has given us. The assurance that our destiny is to be “like him” impels us to set about purifying ourselves, and to do so with the utmost rigour, satisfied with nothing less than to be as pure as God himself (1 John 3:3).

As John sees it, the Christian believer should react to the discovery of any personal impurity with the same shock-horror as God would react to the discovery of a blemish in himself.

The Melody of Joy and Salvation

Adoption was widely practiced in the ancient world, but there was one crucial difference between secular practice and what we see in the New Testament.

In the secular world, adoption was usually for the benefit of the adoptive parents, not for the benefit of the child. For example, a farmer might want help with tilling his land, or a childless couple might want someone to look after them in old age, or an aristocrat might want someone to perpetuate the family name. In the New Testament the benefits are all the other way.

While we may be sure that adoption gives God immense satisfaction, he never adopts in order to meet some need of his own. He adopts us because he loves us, not because he needs us.

And far from exploiting us and subjecting us to a life of drudgery, he showers upon us every spiritual blessing (Ephesians 1:3) and fills our lives with the melody of joy and salvation (Psalm 118:15).