What does the Bible say about being not of this world?

In John 15:18-19, Jesus clearly asserts that if the world hates His followers, it is because they are not of the world, having been chosen out of it. This signifies a profound transformation in those who are united with Christ. They are now part of a new reality—a spiritual existence that aligns them with God rather than the worldly values they once embodied. Being 'not of this world' means that Christians are called to set their minds on things above, emphasizing a life that seeks after Christ rather than the transient pleasures and concerns of earthly life. They are considered citizens of a heavenly kingdom, and their true identity is secured in their relationship with Christ.