The Kingdom is Here

This is the core of the gospel of Christ Jesus; the Kingdom of God is at hand.

This is the main message that Jesus preached when he was on the earth:

Now after John was put in prison, Jesus came to Galilee,
preaching the gospel of the kingdom of God, and saying,
“The time is fulfilled, and the kingdom of God is at hand.
Repent, and believe in the gospel.”

Jesus describes the gospel (the good news) in His own words in Mark 1:15:

The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel.

Jesus did not just come to die on the cross so that we could go to heaven one day. It was a means to establish the Kingdom of God on the earth. That is why He came. Not just to get us into heaven, but first to get heaven into us.