Editors' note: This is the second in a series of posts exploring key doctrines of the Christian faith, and their practical ramifications for everyday life. See my prior interview with D. A. Carson on Christ’s intercession.

In his classic book Knowing God, J. I. Packer wrote:

If you want to judge how well a person understands Christianity, find out how much he makes of the thought of being God’s child, and having God as his Father. If this is not the thought that prompts and controls his worship and prayers and his whole outlook on life, it means that he does not understand Christianity very well at all. . . . “Father” is the Christian name for God.

The doctrine of adoption is indeed integral to the gospel. But in recent years, theological discussion has perhaps been more focused on justification than adoption. And many lay Christians have never considered the rich implications of their adoption. To go deeper into the doctrine of adoption, and especially its practical ramifications, I corresponded with Robert Peterson, professor of systematic theology at Covenant Theological Seminary and author of, among many other books, Adopted By God: From Wayward Sinners to Cherished Children.

What does the doctrine of adoption mean, and where is it most prominently taught in the Bible?

It means that the true and living God, the Creator of the heavens and the earth, by grace has made believers members of his family with all the rights and responsibilities that go with that status. Paul teaches it in many places in, but especially in Romans 8:14-17, 23, 29 and Galatians 3:25-4:7. I agree with John Murray and Sinclair Ferguson that John also teaches it in John 1:12 and 1 John 3:1.

Do the persons of the Trinity play different roles in the doctrine of adoption?

Yes indeed. The Father is the divine lover who predestined us for adoption and sent his Son to rescue us (1 John 3:1; Eph. 1:5; Gal. 4:4). The Son of God is our redeemer who loved us and redeemed us from the law’s threat of punishment by becoming a curse for us (Gal. 4:5; 3:13). “The Spirit of his [the Father’s] Son” (Gal. 4:6), “the Spirit of adoption” (Rom. 8:15) enabled us to cry out to God as Father for salvation (Rom. 8:15) and assures us within that we are God’s children (Rom. 8:16).

The Trinity loves us dearly and planned our adoption, accomplished the work of redemption necessary to adopt us, and applied adoption to us as God’s sons and daughters. This is an important aspect of the triune God’s work of redemption and should occupy a larger place in our worship, whether public, family, or private.

What kinds of people might find special comfort, assurance, or joy in the doctrine of adoption? And how so? 

Men and women who did not have good relationships with their fathers. As a speaker for a men’s conference, I was amazed at the effect of simple messages on adoption on men of many ages. In small groups after the sermons men shared openly how distant their fathers were when the men were growing up. Men wept as the Spirit applied the healing balm of adoption to their heads and hearts. I was moved to be God’s instrument as his Spirit began to fill holes in the hearts of adult men with the tender, biblical message of adoption. I saw similar results in couples’ conferences with both women and men finding help in the doctrine of adoption as laid out in God’s Word.

For those involved in pastoral counseling, when might the doctrine of adoption be of particular value?

There are many answers to this question. One is for people who lack hope. Adoption breeds hope because it not only pertains to eternity (Eph. 1:5), the past (Rom. 8:15), and the present (1 John 3:2, 3), but also the future (1 John 3:2). In the Bible, closely related to the doctrine of adoption is the notion of inheritance: we are God’s children and therefore his heirs (Gal. 3:29; 4:7). God’s true children suffer with him now and will be glorified with him when he returns (Rom. 8:17).

What exactly is our inheritance? Based on the entire biblical story, my answer is: we will inherit the Trinity and the new heavens and new earth (Rom. 8:17; 1 Cor. 3:21-23).

In your own life or in others close to you, where have you seen the doctrine of adoption be of practical value?

I once spoke at a conference whose theme was adoption. When the three speakers talked informally we discovered to our surprise that each of us has unwittingly been drawn to adoption because of a lack in our own relationships with our fathers. God used the biblical teaching on sonship to minister to us and through us to others. In union with Christ, the unique Son of God, I find acceptance by the Father, a new family in heaven and on earth, incentive to live for God, and bright hope for tomorrow. The doctrine of adoption is as warm as the Bible gets. I can hardly think of anything more comforting, more nourishing, more uplifting than the glorious truth that when we trust in Christ, we are made into the sons and daughters of the Creator God.

How would you share the gospel with someone using the doctrine of adoption?

The Bible actually does that very thing. In the first place, our need for salvation is portrayed in the Bible as having to do with our status as slaves to Satan and sin (1 John 3:10; Gal. 4:3, 7). Christ the redeemer gave himself for us slaves and lawbreakers because he loved us. He took the curse (the punishment) of the law that by rights should have fallen on us, not him (Gal. 3:13). Through Christ’s work, we have gone from being slaves to sons (Gal. 4:7).

Parallel to justification, adoption is by grace alone through faith alone in Christ alone (John 1:12; Gal. 3:26). We trust Christ as redeemer in order to be included in God’s family. The results are incredible, including assurance (Rom. 8:16) and paternal discipline (Heb. 12:5-11). By God’s grace, the teaching on adoption enables us to do what it difficult for some of us—to believe that God truly loves us (1 John 4:16).

Can you recommend any resources for further studying the doctrine of adoption?

The best academic resource for TGC readers is Trevor Burke's Adopted into God’s Family: Exploring a Pauline Metaphor. More pastoral treatments include Sinclair Ferguson’s Children of the Living God and my own Adopted by God.