Joh 18:36 Jesus answered, My kingdom is not of this world:…
1Co 3:16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
1Co 3:17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.
Tit_3:5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;
From this we can deduce that when we become a child of The Father the following happens:
Our spirit is renew so that it is no longer defiled by sin,
Because of this it is part of The Kingdom of God because God places the presence of His Spirit it to mark us as belonging to God,
Our spirit then becomes a place where the presence of God resides,
This is why it is called a temple of The Holy Spirit and because it is a temple of God it is holy to Him.
This temple resides in our soul and body. The body has been defiled by sin this is why it must die because it cannot enter heaven because heaven is undefiled and the body is defiled. The soul is the point of contact between the spirit and the body and it is also defiled by sin and is not needed in heaven so it does not go to heaven. This leaves our spirit which has been regenerated by God so is undefiled, pure and holy to God which means it can enter heaven.
The miracle is this pure, holy, undefiled spirit is placed in a defiled body which is why the soul necessary so the body does not have direct contact with the spirit to defiled by it.
So how should we live seeing we have a pure, holy, undefiled spirit in a body of defiled flesh?
We must prevent anything entering us or affecting us in any way that would defile our spirit and cause us to bring the Kingdom of God, which is in us, into disrepute.
You can see that what we do directly affects The Kingdom of God in some way which is why we are told to walk circumspectly, examining everything we do in the light of its effect on The Kingdom of God. Matthew 6:33 applies.
So Jesus asks:
"what do you think of each day?
What do you accept as inputs into your life?
How do they affect My Kingdom?
Now you know why you are told to be holy!
How you appreciate my holiness in you will determine how holy you are.
How holy you desire to be will determine what you allow into your life.
What you allow into your life will determine your salvation.