The modern Church is in grave danger of forgetting the distinctiveness of her gospel and the glorious isolation of her position…The first readers of the Epistle were subject to a similar danger, though it arose from a somewhat different cause. Today we are no longer subject to persecution; but the danger is fundamentally the same. The world’s friendship may be even more disastrous than the world’s hatred. The readers of First Peter were tempted to relinquish what was distinctive in their faith in order to avoid the hostility of their heathen neighbors; we are tempted to do the same thing because the superficial respectability of modern life has put a gloss of polite convention over the profound differences that divined the inner lives of men. We, as well as the first readers of the Epistle, need to be told that this world is lost in sin, that the blood of Christ has ransomed an elect race from the city of destruction, that the high privileges of the Christian calling demand spotless purity and unswerving courage.
–J. Gresham Machen, The New Testament: An Introduction to its Literature and History, pp. 252-53 (emphases added)