16 The Spirit Himself bears witness with our spirit that we are children of God, 17 and if children, then heirs—heirs of God and fellow heirs with Christ, provided we suffer with Him in order that we may also be glorified with Him. ~ Romans 8:16-17
We, our family, were in the process of adopting a little boy several years ago, but before the adoption papers could be fully processed, his mother came and took him back. He enjoyed all the pleasures and all the rights of being our son. Why? Because to us, he was our son. To our daughters, he was their little brother. Even now, whenever we get to see him, he still calls us mom and dad, and our daughters call him their little brother.
It is the same with God; we are called sons or children of God, and we enjoy all of the rights and benefits of being children of God. Siblings with the LORD Jesus and joint heirs with Him. As Paul advocated in the verse above. This is one of the mysteries of God. You must understand that God calls those things that are not as if they were. He proclaims the end from the beginning. Meaning that He sees us as His children because He sees the end result.
If we had achieved sonship already, then that sonship could never be taken away from us because Jesus warned us to abide in Him. If we don’t abide in Him, we will be cut off and thrown into (John 15:1-8). This is why each of the authors and early disciples referred to themselves as slaves to Christ. This makes what Jesus said a lot clearer:
35 The slave does not remain in the house forever; the son remains forever.
John 8:35
Now we can better understand that if we had achieved the sonship, that sonship could in no way be reversed because the son remains forever.
Peace. Love. Go Forth and Aim For Sonship.