God the Father and the Son are one spirit. That’s how they become one. This does not mean that the Father and the Son are one. The Father is the Father and the Son is the Son. As the Father and the Son are one, so we must be one – John 17:21. And so we become one soul.
For we have one God, the Father; We have one Lord, Jesus Christ. (1 Corinthians 8: 6)
This is eternal life, that they may know you, the only true God, and Jesus Christ, whom you have sent. (John 17: 3)
Even as you, Father, are in me, and I in you, that they also may be in us. (John 17:21)
We now see through the mirror; Then face to face. Now I know in part; Then I shall know fully, even as I am fully known. (1 Corinthians 13:12)
Jesus Christ is the image of the invisible God. (Colossians 1:15)
The Father abides in the Son and does the works. (John 14:10)
God is the Spirit. (John 4:24)
Now you will know God the Father through Jesus Christ. In the resurrection, we will fully know God the Father.
God is Spirit = Spirit of Son = Holy Spirit = Spirit of God.
God is the spirit. This spirit is in the Son as well. This same spirit is in the Holy Spirit, and this spirit is in the prophets. This spirit is in the Apostles as well. This is the same spirit that comes to man.
“There is no God who does not abide in the teaching of Christ but goes beyond it. He who abides in his teaching has both the Father and the Son.” (2 John 1: 9)