Romans 8:16-17; Romans 8:21; Romans 9:7-8
The Spirit Himself testifies with our spirit that we are children of God,
and if children, heirs also, heirs of God and fellow heirs with Christ, if indeed we suffer with Him so that we may also be glorified with Him.
that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God.
nor are they all children because they are Abraham's descendants, but: "THROUGH ISAAC YOUR DESCENDANTS WILL BE NAMED."
That is, it is not the children of the flesh who are children of God, but the children of the promise are regarded as descendants.