I often remember that God is our Father. His fatherhood reminds me that He loves us, cares for us, provides for us, teaches us and disciplines us. But strangely, I rarely reflect that I’m His son. When we think of God’s ‘son’, we probably all think of Jesus, and most of us stop there. We forget that God calls every Christian believer His ‘sons’, or His ‘children’. But we mustn’t forget. As John put it, ‘How great is the love the Father has lavished on us, that we should be called children of God!’ (1 John 3:1).

Adoption and sonship are mentioned many times in the Bible, though two passages are central: Romans 8:14–17 and Galatians 3:26–4:7. You may be familiar with them but read them slowly and carefully. Feel the majesty of these truths:

Romans 8:14–17: …those who are led by the Spirit of God are sons of God… The Spirit himself testifies with our spirit that we are God’s children. Now if we are children, then we are heirs—heirs of God and co-heirs with Christ…

Galatians 3:26–4:7: You are all sons of God through faith in Christ Jesus… God sent his Son… to redeem those under law, that we might receive the full rights of sons. Because you are sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, “Abba, Father.” So you are no longer a slave, but a son; and since you are a son, God has made you also an heir.

Can you feel the wonder of Paul’s words? We, who were once slaves to sin, have been adopted as sons of the living God! So let’s look at four astonishing truths that adoption teaches us.

We know we are free

Adoption doesn’t just mean we have a new status as God’s children. It also means we have lost our old status as slaves (John 8:35–36, Gal. 4:7). Adoption sets us free.

This picture was very familiar to Paul’s first-century hearers. In Graeco-Roman culture, sometimes a wealthy man without heirs would adopt his most trusted slave as his son so that the slave would inherit the estate (more on that later). But his adoption also meant he was no longer a slave. He was now free.

In fact, he was more than free. Roman slaves could be freed without the master needing to adopt them. When that happened, the slave would officially be known as a freedman. As a freedman, he would have some rights (he could vote, for example), but he wasn’t a full citizen and was barred from public office and higher ranks. But all that changed if a slave was adopted. An adopted slave was never known as a freedman. He was simply a son, and the restrictions on freedmen didn’t apply to him. As a son, he was free indeed.

As adopted children of God, we are not second-class citizens. We are not partly free, or mostly free. We are free indeed.

We know we will inherit

The primary purpose of adoption in Graeco-Roman society was to facilitate inheritance. Family was vital, and it was unthinkable that an estate would not be kept within the family. So, if someone were likely to die without an heir, they wouldn’t just write a will to leave their estate to someone outside the family. Instead, they would adopt their beneficiary into the family.

The Roman emperors typified this. If they had no sons, they would appoint a successor through adoption. Emperor Nerva adopted Trajan as his successor, and then Trajan, in turn, adopted Hadrian. Likewise, our spiritual adoption means we are fully part of God’s family, and it guarantees our inheritance.

A few days ago, I was reading an article in the New York Times about a family who had a son, then adopted more children. Before going through with the adoption, they sat down with their son and asked him his thoughts. They felt it was important he understood that if they adopted these children, he would be sharing his inheritance with them. Was that OK? Similarly, as adopted children, we share in Christ’s glory as His co-heirs (Rom. 8:16–17).

We know we are secure

God really wants us to grasp that we are His children — so much so that He didn’t just teach us so in His Word, but He also gives us the Spirit to testify to us of our sonship (Romans 8:15–17). Our adoption guarantees our inheritance.

A child that is fostered will always be less secure than one that is adopted, no matter how loving the foster-parents. But Christians are not fostered. We are adopted!

That’s why Romans 8:15 emphasises that as adopted children we need not fear. Our status, our inheritance and our relationship have been firmly established, not on a temporary basis, but on a permanent one.

We know we belong

But although adoption is how we inherit Christ’s glory, that certainly isn’t the only purpose of adoption. Even more than that, adoption brings us into a family where we belong. There are two aspects to this.

First, our adoption means that God is our Father, and Christ our Brother (Hebrews 2:11–12). We’re not equal with Christ, of course. His sonship is different from ours, because He is the firstborn, and our sonship derives from His (Romans 8:29). But we’re no less a son than He is. By adoption, we’re fully part of the divine family.

I confess I sometimes find this difficult to believe. At times, I feel as though I don’t belong. How can I consider Jesus as my brother? How can I be a co-heir with Him, and share his glory? You might think such thoughts show a godly humility, but the opposite is true. When I think that I don’t belong, it’s because I think too much about myself and not enough of God. When I think about myself, of course I would conclude that I don’t belong. How could I? That’s not humility, that’s reality! But when I think about God, I remember that I belong only because of what He has done. He has made me a brother, a co-heir and a son, through adoption. By nature, I could never belong, but by adoption, I do belong!

Secondly, our adoption also means that we are part of an enormous family here on earth and an even bigger family in heaven. We have brothers and sisters from every nation. The New Testament hardly ever says that I am a child of God, but it frequently testifies that we are children of God. Do you see the difference? My adoption into a family means I no longer belong to myself, but I’m part of something much bigger and much more glorious.

And, by God’s grace, that is where we belong. We’re free, we’re secure, we’ll inherit and we belong. It’s no wonder Jim Packer said adoption is ‘the highest privilege that the gospel offers’.