The spirit of Christ and the Holy Spirit have various misconception. We often interchange them in our interpretations of the scriptures. This is the only means by which we understand. If a passage is talking about the Holy Spirit or spirit. Is that the letter “s” is in uppercase or lowercase. Hence the reason for a careful meditation in order to understand what the Bible is really saying. We cannot really judge by the translations as most translations were translated based on the translator’s understanding of the scriptures.

The Holy Spirit versus the spirit of Christ

The Holy Spirit is the third person of the Godhead. He is God, an agent of power. He is not the spirit of Christ so much as He is not the spirit of Adam. Jesus Christ means Jesus the anointed, the question now is “will God anoint Himself?” certainly, anyone anointed has someone who anointed Him and that person is greater than him. When God created Adam, He gave him His spirit which made Adam to have God’s likeness and that doesn’t make him to be God. In the same way, the spirit of Christ unifies us with Christ Jesus. Just as the spirit of Adam linked us back to Adam.
When we gave our lives to Christ we received His spirit which Adam lost when he sinned. Jesus was born the same way Adam was born spiritually alive. But the Holy Spirit was not mentioned until when Jesus was about starting His ministry during His baptism.

 You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him. 

Romans 8:9

The flesh versus the spirit of Christ

As understood earlier the flesh he is talking about is not this physical flesh. The comparison being made is between a life subject to the leading of sin and the life subject to the leading of the spirit of Christ. We are no longer in the flesh. It means, no longer in the old life given to us by Adam when we were born. But rather in the spirit, the new life we received when we surrendered to Jesus. This is why there is another event of receiving the baptism of the Holy Spirit separate from the new birth (receiving the spirit).

The spirit and our salvation

He mentioned spirit of God and spirit of Christ. Both are still in the same flow of thought. Because God gave Adam His spirit which qualifies him to have God’s likeness and Jesus is the last Adam. We can understand this further because there are movements of people that doesn’t belief in the Holy Spirit as the Pentecostal believes. Although this does not affect them being a Christian. Because the prerequisite for salvation is not believing in the Holy Spirit but in the Lordship and resurrection of Jesus Christ. That is simply receiving the spirit of Christ which makes us to belong to Him.

 But to all who did receive him, who believed in his name, he gave the right to become children of God,

John 1:12

Conclusion

We belong to Him not because we can do miracles but because we have His spirit. Although, some people still commit sin. Despite the fact that they claim to have the Holy Spirit, speak with tongues and prophesy. These show us a clear distinction between having the spirit of Christ and Holy Spirit. Wonder why Jesus said

“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven.²² On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ ²³ And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’

Matthew 7:21-23

It is the spirit of Christ in us that bears the fruit. It make us fit for the kingdom of God not the Holy Spirit. We can do works for God and still miss heaven. Because we have lost the substance which is the spirit of Christ.