Galatians 3: 26-29 --For ye are all the children of God by faith in Christ Jesus. For as many of you as have been baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus. And if ye [be] Christ's, then are ye Abraham's seed, and heirs according to the promise.
God, from the foundation of the world, knew you, ordained you, and mandated your purpose in the earth. Upon your birth, you were given a name who was synonymous to who your parents knew you were. That name stuck with you, even until now. However, upon your re-birth, and regeneration through Jesus Christ, you were given a new name. That name is a child of God.
What does it mean to be a child of God? According to God's Word, we are one with Him. We are Abraham's seed and an heir. That means we have a promised inheritance from God that is greater than anything we could receive from this world. It is an identity that can never be taken away.
There are many in the Bible that had one name upon birth, but after getting a greater insight and a greater sense of purpose as to who God was in their lives, their names changed. Jesus immediately gave Simon Bar-jona the name, Peter meaning Rock in the Greek, after He gained insight into who Jesus really was. As a matter of fact, Jesus said to him, "Blessed are you, Simon Bar-jona, For flesh and blood have not revealed this to you, but My Father Who is in heaven" (Matthew 16:17). When Abram and Sarai took hold of the knowledge and insight into their greatest purpose of being the mother and father among many nations, it in turn, caused a dramatic change in their characters-thus the given names Abraham and Sarah (Genesis 17:5, 15).