Romans 8:9
You, however, are controlled not by the flesh, but by the Spirit, if the Spirit of God lives in you. And if anyone does not have the Spirit of Christ,
he does not belong to Christ.
Romans 8:11
And if the Spirit of Him who raised Jesus from the dead is living in you, He who raised Christ Jesus from the dead will also give life to your mortal bodies through His Spirit, who lives in you.
1 Corinthians 3:16
Do you not know that you yourselves are God's temple, and that God's Spirit dwells in you?
John 3:3- the kingdom of God, heaven and Christ are the same kingdom.
Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again.”
Below Jesus contrasts the two- hell and the kingdom.
Mark 9:47
And if your eye causes you to sin, pluck it out. It is better for you to enter the kingdom of God with one eye than to have two eyes and be thrown into hell,
So one must have the spirit of God in them via the new birth, born again to be in the kingdom and have eternal life- salvation. See John 1:12-13.