Matthew 13:29-30
King James Version (KJV)
29But he said, Nay; lest while ye gather up the tares, ye root up also the wheat with them. 30Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.
A Carnal Christian will look the same as an unsaved person in the eyes of man, let them grow together because we are not smart enough to tell the difference. If we start picking and choosing and trying to say who is Saved and who isnt we might uproot the wheat because we cant tell the difference. Keep on Preaching and teaching the Word and let the Holy Spirit work in the hearts of those that you would look at there lifes and thru your eyes believe that they do not possess Christ. God says we cant tell the difference.