A selection of verses showing the inevitable conflict between our natural way of living (the "flesh") and God's way (the "spirit").

Jesus makes it clear that there is a distinction between "flesh" and "spirit":

John 3 verse 6
6  That which is born of the flesh is flesh. That which is born of the Spirit is spirit.

He also points out the consequences of both ways of life. He tells us that we can be "in the spirit" by listening to what he says:

John 6 verse 63
63  It is the spirit who gives life. The flesh profits nothing. The words that I speak to you are spirit, and are life.

The letters to the Romans and Galatians give us the consequences of both ways of life:

Romans 8 verse 13
13 For if you live after the flesh, you must die; but if by the Spirit you put to death the deeds of the body, you will live.

Galatians 6 verse 8
8 For he who sows to his own flesh will from the flesh reap corruption. But he who sows to the Spirit will from the Spirit reap eternal life.

The letter to the Galatians tells us that there is tension between "flesh" and "spirit" and that naturally speaking the "flesh" will be the easier option:

Galatians 5 verse 17
17 For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, that you may not do the things that you desire.