Adoption into the family of God is a wonderful thing. Not only do we have brothers and sisters in Christ who we can have fellowship with, we also have God as our Father. John 1:12 says that those who believe in Jesus have been given the right to be called children of God.
Why is adoption not preached enough? Adoption is Biblical yet neglected. Voddie Baucham has a sermon on the doctrine of adoption which was preached at Pray's Mill Baptist Church in Douglasville, Ga, where Josh Buice is the pastor.