You may have heard this popular saying in Christian circles: "We are in the world but not of the world." This saying isn't in the Bible, but it does summarize what the Bible says on the subject. The idea is a central theme that runs through Jesus's high-priestly prayer for his disciples recorded in John 17.
 
I will remain in the world no longer, but they are still in the world, and I am coming to you. Holy Father, protect them by the power of your name, the name you gave me, so that they may be one as we are one…
 
I have given them your word and the world has hated them, for they are not of the world any more than I am of the world. My prayer is not that you take them out of the world but that you protect them from the evil one. They are not of the world, even as I am not of it. Sanctify them by the truth; your word is truth(verses 11, 14-17).
 
Yes, we live in this world, but we are not of it. We do not belong. We are, as Peter wrote, "foreigners and exiles" (1 Peter 2:11), or "aliens and strangers" (NASB). We do not fit in anymore.
 
When the Bible speaks of the world, it is not referring to planet Earth. Earth and all of God’s creation will be restored. There will be a new heaven and a new earth. Right now creation waits to be freed from the curse that resulted from Adam and Eve's sin. Paul brought out this point in his letter to the Romans.
 
The creation was subjected to frustration, not by its own choice, but by the will of the one who subjected it, in hope that the creation itself will be liberated from its bondage to decay and brought into the freedom and glory of the children of God (Romans 8:20, 21).