If you want to see more of the beauty of adoption, consider this brief quotation from Dr. C.F.W. Walther:
"Every Christian may apply to himself the declaration of God: 'This is My beloved Son, in whom I am well pleased."
If you are a Christian, God speaks these amazing words over you: "You are My beloved child, in whom I am well pleased!" He doesn't speak these words over you because you've earned them. You could never do enough to earn these words of love. God speaks these words over you because of who Jesus is for you.
When God the Father spoke these great words over His Son (Matthew 3:17), it was the day that Jesus began his public ministry as the Messiah. Here's why this is significant: what is true of the Messiah is true of his people. Jesus was the faithful son who always did the will of his Father. Never once did he disobey or disappoint Him. All of his obedience from his birth in the manger to his death on the cross was perfect in thought, word, and deed. And as our Messiah, he obeyed for us so that the same words that were spoken over him on that wonderful day could be spoken over us.
Living as a Christian involves learning to live each day knowing that God the Father thinks of you as His beloved child in whom He is well pleased. Those who learn to live in the reality of God's loving pleasure will find that circumstances no longer control them. They find that they are able to deal with the difficulties of life with confidence and humility. To be adopted by God is to enter into a family relationship where all of God's children are treated even as He treats His Beloved Son. If you are being loved by God like this, you'll not only desire to love others like this, you'll also be empowered to do so.
Think about the implications this has for families who adopt.