God decided in advance to adopt us into his own family by bringing us to himself through Jesus Christ. This is what he wanted to do, and it gave him great pleasure.
Eph. 1:5 NLT
In Roman law, the patriarch of the family (pater familias) who did not have an heir could engraft another male into his family line by adoption. The adopted son would have all the rights and privileges of a biological child. The family’s leadership, business, finances, reputation, etc., would all pass to this adult male son who had been given this new status as heir of the family.
In spiritual terms, adoption is the act whereby God makes his people his children, members of his family (Eph. 1:5). By spiritual adoption, believers are accepted in Christ and thereby receive all the riches of Christ’s work and glory. Adopted status belongs to all who receive Christ by being born from above (John 1:12). Our adopted status means that in and through Christ, God loves us as he loves his one and only Son. The Lord chooses to bless us now with Christ’s spiritual riches and will share with us all the glory of Christ in heaven (Rom. 8:17, 38–39).
We are adopted into God’s family through the resurrection of Christ from the dead in which he paid all our obligations to sin, the law, and the devil, in whose family we once lived. Our old status lies in his tomb. A new status is ours through his resurrection.
Sinclair Ferguson, Children of the Living God (Carlisle, PA: The Banner of Truth Trust, 1989), 37.