Romans 12:2

If a Christian can possibly be saved while he conforms to this world, it must, in any case, be so as by fire. Such a bare salvation is almost as much to be dreaded as desired. Reader, do you wish to leave this world in the darkness of a despairing deathbed, and enter heaven as a shipwrecked mariner climbs the rocks of his native country?

Then be worldly; be mixed up with worshippers of Mammon, and refuse to go outside the camp bearing Christ’s reproach. But would you desire a heaven below as well as a heaven above? Would you comprehend with all saints what are the heights and depths, and know the love of Christ which passeth knowledge?

Would you receive an abundant entrance into the joy of your Lord? Then come ye out from among them, and be ye separate, and touch not the unclean thing. Would you attain the full assurance of faith? You cannot gain it while you associate with sinners. Would you flame with passionate love?

Your love will be dampened by the drenchings of godless society. You cannot become a great Christian—you may be a babe in grace, but you can never be a perfect man in Christ Jesus while you yield yourself to the worldly principles and practices of people of the world.

It is not good for an heir of heaven to be close friends with the heirs of hell. It looks bad when a courtier is too intimate with his king’s enemies. Even small inconsistencies are dangerous. Little thorns make large blisters, little moths destroy fine garments, and little frivolities and minor deceptions will rob religion of a thousand joys.

O professing Christian, too little separated from sinners, you do not know what you lose by your conformity to the world. It cuts the tendons of your strength and makes you creep where you ought to run. Then, for your own comfort's sake, and for the sake of your growth in grace, if you are a Christian, be a Christian, and be a marked and distinct one.