Question: "What does it mean that Christians are adopted by God?"
Answer: To adopt someone is to make that person a legal son or daughter. Adoption is one of the metaphors used in the Bible to explain how Christians are brought into the family of God. Jesus came “that we might receive adoption to sonship” (Galatians 4:5), and He was successful: “You received God’s Spirit when he adopted you as his own children” (Romans 8:15, NLT).
The Bible also uses the metaphor of being “born again” into God’s family (John 3:3), which seems to be at odds with the concept of adoption because, normally, either a person is born into a family or adopted, not both. We shouldn’t make too much of the difference, however, because both of these concepts are metaphors and should not be played against each other.
Adoption was not common in the Jewish world. A person’s standing was based on his birth. This is the reason that, if a man died, his brother was supposed to marry the widow. The first son to be born of the new marriage would be legally considered the son of the dead brother so that his family line would continue. There was never any thought of the widow adopting a son to carry on the family name. In John 3, Jesus is speaking to Nicodemus, a Jewish leader, and He uses the Jewish concept of being born again (or born from above) to explain how one is brought into God’s family.
In the Roman world, adoption was a significant and common practice. Today, we can write a will and leave our wealth and property to anyone we want, male or female. In the Roman world, with few exceptions, a man had to pass his wealth on to his son(s). If a man had no sons or if he felt that his sons were incapable of managing his wealth or were unworthy of it, he would have to adopt someone who would make a worthy son. These adoptions were not infant adoptions as is common today. Older boys and adult men were normally adopted. In some cases, the adoptee might even be older than the man who was adopting him. When the adoption was legally approved, the adoptee would have all his debts cancelled and he would receive a new name. He would be the legal son of his adoptive father and entitled to all the rights and benefits of a son. A father could disown his natural-born son, but an adoption was irreversible.
In the book Ben-Hur: A Tale of the Christ and the movie starring Charleton Heston, we see a vivid portrayal of Roman adoption. In the movie, Judah Ben-Hur (a Jew) has been imprisoned on a Roman galley ship as a rower. When the ship sinks in battle, Judah escapes and saves the life of a Roman commander, Arrius. Arrius’s only son has been killed, and he ultimately adopts Judah, who is pardoned for his supposed crimes. He is also given a new name, “young Arrius,” and has all the rights of inheritance. In the scene where the adoption is announced, Arrius takes off his ancestral signet ring and gives it to young Arrius. Young Arrius says that he has received “a new life, a new home, a new father.”
Paul, writing to Roman audiences, uses the metaphor of adoption, which a Roman audience would have understood. Galatians 4:3–7 says, “So also, when we were children, we were enslaved under the basic principles of the world. But when the time had fully come, God sent His Son, born of a woman, born under the Law, to redeem those under the Law, that we might receive our adoption as sons. And because you are sons, God sent the Spirit of His Son into our hearts, crying out, ‘Abba, Father!’ So you are no longer a slave, but a son; and since you are a son, you are also an heir through God.” In this passage, Christians are born enslaved, but Jesus buys them out of slavery and they are adopted by the Father and given the Spirit, so now they are heirs.
When we come to faith in Christ, our debts are cancelled, we are given a new name, and we are given all the rights that heirs of God possess. One difference from Roman adoption is that Christians are not adopted because God thinks they will make worthy heirs. God adopts people who are completely unworthy, because He adopts on the basis of His grace.
So, Christians have been born into God’s family (using a Jewish metaphor) and adopted into God’s family (using a Roman metaphor). The end result is the same; Christians are forever part of God’s family.