"But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear:" 1 Peter 3:15 (KJV)
What Is Sanctification? Part 6
Sanctification or holiness is a separation from the ways of the world into the ways of God. Our level of commitment to be holy determines how much we look or not like the world.
So you have Christians that were born again, but they were never disciple into this second work of grace of sanctification. They join denominations that are extremely liberal in their doctrines and that is obviously appealing to the desires of the flesh. In certain denominations you can be a Christian and still do what you like to do.
So it is ok to drink, is ok to party in a secular way, is ok to go to clubs, is ok to watch R Rated movies, is ok to see vulgar concerts, is ok to listen to secular music, is ok to dress in a sensual way, is ok to use profanity, is ok to lie, is ok to steal, is ok to fornicate, is ok to engage in homosexual lifestyles, is ok to gossip, is ok to be bitter, is ok to be un-forgiven etc., etc.
As you can see, this is a Christian that pretty much looks like the world that surrounds him/her; I will take it further and say that, this is a Christian that looks worst than the world. First Thessalonians 5:23 again, is key,
“Now may the God of peace Himself sanctify you completely; and may your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ.” NKJV
The word Blameless means “Without fault”. That means that you can’t be accused of being involved in these various things that the world is involved with. Again, that does not mean that you are morally perfect, but you do all you need to do to stay away from those things that activate your sinful nature.