“Therefore if any man be in Christ, he is a new creature; old things are passed away; behold, all things are become new.” 2 Corinthians 5:17 (Concordia Translation)
This process describes those who have become God's people by making a full consecration of themselves and then being begotten of the Holy Spirit as new creatures in Christ. Conversion, belief and reformation of life does not necessarily make a Christian in the Biblical sense. From God's standpoint, the consecrated and begotten are “new creatures,” having the old body, but a new will–the will of Christ. In the “First Resurrection” this new creature will receive an appropriate new body – a spirit body in the heavenly realm.
“Instead of being moulded to this world, have your mind renewed, and so be transformed in nature, able to make out what the will of God is, namely, what is good and acceptable to Him and perfect.” Romans 12:2 (Moffatt Translation)
“For we are His workmanship, created in Christ Jesus to perfect works. which God hath before ordained that we should walk in them.” Ephesians 2:10 (KJV)