Changing is not a suggestion. It’s imperative. It is a command. “Do not be conformed,” (Romans 12:2) is an imperative in the Greek, as it is in the English.
Zodhiates paraphrases this way, “Stop being molded by the external and fleeting fashions of this age, but undergo a deep inner change by the qualitative renewing of your mind.”
The underlying Greek word is used only one other time in the New Testament: “As obedient children, do not conform to the evil desires you had when you lived in ignorance. But just as he who called you is holy, so be holy in all you do.” 1 Peter 1:14–15 (NIV)
Instead of conformity to the world, holiness is commanded. Holiness is not an advanced class for super Christians. It is a required class for all Christians. Holiness essentially means, “different.”
The Hebrew word for holiness means, “to cut.” Imagine cutting the fat off of a steak. This is what it means to be holy—to cut off and separate from. We are commanded not to conform to this world but to be holy—cut off or separate from the sin in this world.
Being conformed has to do with an outward experience that does not reflect that which is within.
If I were to behave in a way that is ugly, you ought to be able to say, “That is not really who Johnny Hunt is.”
For example, I had a man call me one time and say, “Pastor Johnny, why are you sending us these demanding emails?”
I hadn’t sent any emails.
As we talked, the story was uncovered. Someone—let’s call him Bob—had created an email account in my name. Bob sent an email to a pulpit committee along with his own resume. He wrote a glowing endorsement of himself and signed it with my name.
When the committee did not respond, he emailed again, insisting that they take a look at his resume. He was quite forceful in his insistence. In the providence of God, one of the people on the committee knew me personally. He picked up the phone and called, saying, “Pastor Johnny, this doesn’t sound like you. Why are you sending these demanding emails?”
He thought I was acting in a way that was not consistent with the real me. Of course, in this case, it was not me at all.
This is what it means to, “be not conformed.” It means that we are to behave like who we really are, not like the world is trying to get us to behave.
Spiros Zodhiates, The Complete Word Study Dictionary: New Testament (Chattanooga, TN: AMG Publishers, 2000).