Romans 8

As Paul writes to the Roman converts, especially the Jewish converts, to me it seem he is trying to emphasize that at one time, he too, strived to live the law of Moses, but recognized that much of its works were outward and not spiritual.  In my mind, he even suggests that in living this law he committed sin that was not necessarily contrary to the law of Moses but offensive to God.

And example that came to me was the Mosaic law or developed law that one must not eat unless they wash their hands first.  This is a valid health law that benefitted the Jews, but it had no bearing on eternal life.  Remember the Pharisees came asking the Savior -

"Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread.
3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?"  (New Testament | Matthew 15:2 - 3)

In other words, why do you transgress spiritual laws that impact eternity.  It is to this reasoning, Paul wrote the Romans -

"For I delight in the law of God after the inward man..."  (New Testament | Romans 7:22)

This is the doctrine and laws of Christ.  The spiritual taught by the Holy Ghost.

"For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
6 For to be carnally minded is death; but to be spiritually minded is life and peace."  (New Testament | Romans 8:5 - 6)

Obviously, Paul is teaching inward (of the heart) righteousness and obedience.

Paul then teaches the very reason or plan or purpose of this earth life in striving for righteousness -

"For as many as are led by the Spirit of God, they are the sons of God."  (New Testament | Romans 8:14)

In my mind, "sons of God" in this case are those that Christ gives eternal life through His grace.  But also

"The Spirit itself beareth witness with our spirit, that we are the children of God:
17 And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together."  (New Testament | Romans 8:16 - 17)

These words literally suggest that God is our Father in Heaven and that we can become heirs.