The Bible does not hesitate to condemn worldliness for the serious sin that it is. Worldliness is any preoccupation with or interest in the temporal system of life that places anything perishable before that which is eternal. Since believers are not part of the world system (John John 15:19), they must not act as though they were. Do not be conformed to this world, wrote the apostle Paul, but be transformed by the renewing of your mind, so that you may prove what the will of God is, that which is good and acceptable and perfect (Rom. Rom. 12:2).1
1 John MacArthur, Revelation 1-11 : The MacArthur New Testament Commentary (Chicago, IL: Moody Press, 1999), 82.