"My kingdom is not of this world ..." (John 18:36)

"My kingdom is not of this world. If it were, my servants would fight to prevent my arrest by the Jewish leaders. But now my kingdom is from another place." (John 18:36)

Why is Jesus saying this?

Jesus is responding to Pilate, who is challenging Jesus' authority. And Jesus is documenting that his authority lies elsewhere, not within the physical world.

In this particular part of the exchange, Pilate said:
"Am I a Jew?" Pilate replied. "Your own people and chief priests handed you over to me. What is it you have done?" (John 18:35)
So we can see from this text that the institutional temple priests were responsible for Jesus' arrest and him being handed over to Pilate, who was the regional ruler for the Romans.

Jesus wasn't arrested and tried for being a rebel. Rather, this was about envy: A particular institutional leader - the High Priest Caiaphus - was envious of Jesus' authority.

And Pilate asks directly, what Jesus might have done to deserve this envy?

As such, Jesus' response is clear - Jesus' authority does not lie within the physical dimension. It lay within the spiritual realm. That place outside of the world of envy.

What did Jesus mean by 'my kingdom'?

Does this mean that Jesus is God?

Or does he mean "my kingdom" as though he is in charge in heaven?

Jesus is referring to domain here. The Greek word being translated to "kingdom" is βασιλεία (basileia). This can mean authority or rulership, but it can also mean - when referring "concretely" - to "a realm" according to Thayer's lexicon.

We might compare this to how someone might refer to their house: "I live in a brown two-story house." The person is not necessarily saying that the house belongs to him directly - he could be renting the house. Rather, he is referring to his domicile: It is the place he considers his home.

At the same time, Jesus is inferring that he has authority within the spiritual realm. What kind of authority is that?

It is being the Supreme Being's loving servant. Just consider this statement:
"But from now on, the Son of Man [Servant of Humanity] will be seated at the right hand of the mighty God.” (Luke 22:69)
When a person says they will be seated at the "right hand" of someone else, what do they mean? They mean that they are their special (or intimate) servant - their "right-hand man" so to speak.

In other words, Jesus saw his authority in relation to the Supreme Being.

This might be compared to a small child feeling very big and strong because his father is big and strong. Because they are on the same "team" so to speak - the son reflects the authority of his father.

This doesn't mean the son is the father.

But Jesus' statement indicates something that is hidden from the view of Pilate, the institutional temple priests, and many ecclesiastical institutions and their teachers:

The fact that Jesus' authority is derived from a loving relationship.

It is not as if Jesus is feeling he is so great because God is so great. It is not a position of power that Jesus is feeling about "my kingdom."

Rather, it is an exchange of a loving relationship with the Supreme Being. This gives Jesus authority. Because he is loving God and wanting to please God, he wants to do God's will.

What kind of authority did Jesus have?

We might compare this to how a spouse might represent their spouse in some type of public situation. They may just be married, but when it comes to representation, everyone will accept that a spouse has the authority to represent their spouse in a situation where their spouse is not present.

In the same way, because Jesus has an intimate relationship with God, he can speak with authority about his home outside the physical realm. He can speak with authority about God and God's realm.

Yes, the Supreme Being created everything. Everything is part of His kingdom. Therefore, a person can be in the spiritual realm even when they are still within their physical body in the physical world if they are living within a loving service relationship with the Supreme Being.

Such a person might appear as though they are in the physical world, but they are really in the spiritual realm. Their entire life is driven by wanting to please God. Jesus will return to the spiritual dimension after he leaves his physical body. But he is functionally within the spiritual realm where ever he may be.

The spiritual realm exists where ever and whenever a person has accomplished this instruction by Jesus:
“‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment." (Matt. 22:37-38)

*Here is the translation of these verses from the Lost Gospels of Jesus:
Jesus answered, “My authority is not of this material world. If my authority was of this world, then my followers would have fought to prevent my arrest by the institutional temple officials. As such, my authority is not from this realm.” (John 18:36)