The term “Son of God” refers preeminently to Jesus Christ’s deity (Matt. 11:25-27; 16:16-17). He alone is one in substance and glory with God the Father. Believers in Christ, although “adopted” are never on a par with the uncreated, divine Son of God.
“Adoption” is the term the apostle Paul uses to describe the act of the Holy Spirit whereby the believing sinner becomes a member of God’s family, with all the privileges and obligations of family members.
We were “children of wrath” by nature (Eph. 2:3). However, those upon whom God bestows His saving grace become the “children of God.”
The word adoption in the New Testament means to place as an adult son. It was a term used in the Roman legal practice in the apostle Paul’s day referring to a legal action by which a person takes into his family a child not his own, with the purpose of treating him as and giving him all the privileges of an own son. An adopted child was legally entitled to all rights and privileges of a natural-born child. Paul uses it as an illustration of the act of God giving a believing sinner, who is not His natural child, a position as His adult son in His family. The emphasis is on the legal position of the child of God.
It is the Holy Spirit who is called “the Spirit of adoption” who performs the act of placing the believing sinner as an adult into the family of God. “For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, ‘Abba! Father!’” (Rom. 8:15)
The adopted child lost all rights and privileges in his old family and gained all the rights of a legitimate son in his new family. He got a new father, and he became the heir to his new father’s estate. He became co-heir with the other sons. In the eyes of the law the old life was completely wiped out. All debts were completely cancelled. He was absolutely the son of his new father. It was carried out in the presence of seven witnesses.
What a glorious privilege is ours to be the absolute possession of the Father! We have already as believers in Christ been placed in the family of God and are led by the Holy Spirit as the adult sons of God. The apostle John describes our experience as God’s children who have been born into His family by the new birth (Jn. 1:12; 1 Jn. 3:1-2).
Moreover, Romans 8:23 tells us “we ourselves groan within ourselves, waiting eagerly for our adoption as sons, the redemption of our bodies.” At the Second Coming of Christ our resurrected bodies will be glorified and will then possess all our inheritance that the sonship involves.
Galatians 4:4-6 and Ephesians 1:5 make it clear that we cannot lose our adoption. Because Jesus Christ paid the penalty of our sin debt in full, nothing stands in the way of a just God regenerating a believing sinner and placing him as His child in His family. The Holy Spirit as “the Spirit of adoption” also places a saved sinner in a legal standing in God’s family. The adopted son has all the rights and privileges of God’s only begotten Son. God the Father loves the adopted child just as much as He loves His only begotten Son.
“We are sons of God through faith in Christ Jesus” (Gal. 3:26). As a result of God’s adopting us we are just as eternal and secure in our relationship with Him as His only-begotten Son. All the security and loveliness of God’s Son is ours as His adopted sons. The Holy Spirit imparts to us the divine nature and places us in the family of God in accordance to His unchanging laws.
This is our new standing before the LORD God. He accepts us into His family, who by nature do not belong to it, and places those who are not His sons originally into a right relationship with Him with all the privileges of that new family relationship.
Jesus Christ alone is the Son of God by nature. We can never have the same relationship He has as the unique Son of God. The word “adoption” distinguishes those who are made sons of God from the only-begotten Son of God. The Holy Spirit, however, creates in the believing sinner a new nature. We have not only the new status as sons, but also the heart of true sons. Our adoption is the act of God’s pure goodness and grace of His will to the praise of His glory.