The Spirit Himself [itself, King James Version] bears witness with our spirit that we are children of God, and if children, then heirs—heirs of God and joint heirs with Christ, if indeed we suffer with Him, that we may also be glorified together.
Christians are given the Holy Spirit upon baptism and the laying on of hands (Acts 2:38; 8:17), and that Holy Spirit unites with our spirit in man to give us new life as a child of God.
Here the apostle Paul encourages us with the awesome inheritance that God offers us as joint heirs with Jesus Christ, our Elder Brother. Though Christ inherits all things, He is willing to share all things with us, if we are willing to suffer with Him. Paul goes on to show that even the sufferings are “not worthy to be compared with the glory which shall be revealed in us” (Romans 8:18).
For some thoughts on the incredible inheritance God offers in the Kingdom of God, see the article “Children of God.”