Romans 8:15 (NA28)15 For you have not received a spirit of slavery leading to a spirit of slavery again, but you received the spirit of adoption as sons by whom we cry out, “Abba! Father!” (Romans 8:15 translated from the NA28 Greek text to English)
The Eastern concept of adoption goes deeper than our Western concept. Only the Apostle Paul uses this word in the NT, υἱοθεσίας (huiothesia) translated in the passage above as “adoption.” Paul, being a Roman citizen, no doubt borrowed it from Roman culture since the Jews knew nothing of it.
The Greek huiothesia literally means “son-placing.” While a child possessed nothing and had no rights, during the teenage years there was a public ceremony declaring a child to be an official member of the family. After this “son-placing,” he had full privileges and responsibilities. This was not necessarily a change in relationship–for a Roman father could be just as loving as any other father, and no doubt many fathers had a close relationship with their children. Rather what we see here is a change in position. He was no longer a child; he was a son.