I have two beautiful daughters. The older is next to me as I type this and the younger is upstairs fighting the urge to give in into her nighttime sleep. They are, without question, my daughters and I am proud of them.
We share a lot of time together, we share a home, we share a love to be outside and playing, but one thing we don't share is biology. Neither of my precious girls has my eyes. Neither of them has their mother's freckles.
Both of our girls entered our family through adoption. The older was adopted a few years ago and the younger just a month ago. Even so, they are my daughters and there is no way they could be any more my daughter than they are.
Notice what I typed though: I didn't say they "are" adopted as in present tense. "Adopted" is not their identity. They "were" adopted. Past tense. Done. One day they had one heritage and identity and the next day they had a brand new heritage and identity. (In their cases, each of them came from families that wish they could have been their parents; loving and sacrificial. There was never a time in my daughter’s existence that they were unwanted, either by their birth families or our family.)
They are my daughters. They always will be. I treasure that. I treasure them.
In Galatians 4, Paul describes the relationship God the Father has with those who are his children with the metaphor of adoption. Roman adoption that Paul knew was different in many ways than ours, but that kind of adoption is a beautiful picture of how a Father brings his children into his family. One day they had a heritage and identity that was separate from the Father...excluded...alone. Then, by his grace, he adopted us into his family and into a new identity: welcomed, reconciled, dearly loved, forgiven.
All who entrust themselves by grace to Jesus are adopted into God's family. Past tense. Not a second class member of the family, but a child who is fully loved and accepted. And none of it had to be earned, but it is all given as a gift.
Galatians 4:4–7: But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. And because you are sons, God has sent the Spirit of his Son into our hearts, crying, “Abba! Father!” So you are no longer a slave, but a son, and if a son, then an heir through God. (ESV)