I just came across this and found it a worthy exhortation on how Christians should live in the world but not of the world. It captures some good distinctions. It is certainly applicable given our current cultural and political climate in the United States and elsewhere.
The Epistle of Mathetes to Diognetus¹
For the Christians are distinguished from other men neither by country, nor language, nor the customs which they observe. For they neither inhabit cities of their own, nor employ a peculiar form of speech, nor lead a life which is marked out by any singularity. The course of conduct which they follow has not been devised by any speculation or deliberation of inquisitive men; nor do they, like some, proclaim themselves the advocates of any merely human doctrines. But, inhabiting Greek as well as barbarian cities, according as the lot of each of them has determined, and following the customs of the natives in respect to clothing, food, and the rest of their ordinary conduct, they display to us their wonderful and confessedly striking method of life. They dwell in their own countries, but simply as sojourners. As citizens, they share in all things with others, and yet endure all things as if foreigners. Every foreign land is to them as their native country, and every land of their birth as a land of strangers. They marry, as do all [others]; they beget children; but they do not destroy their offspring. They have a common table, but not a common bed. They are in the flesh, but they do not live after the flesh. (2 Corinthians 10:3) They pass their days on earth, but they are citizens of heaven. (Philippians 3:20) They obey the prescribed laws, and at the same time surpass the laws by their lives. They love all men, and are persecuted by all. They are unknown and condemned; they are put to death, and restored to life. (2 Corinthians 6:9) They are poor, yet make many rich; (2 Corinthians 6:10) they are in lack of all things, and yet abound in all; they are dishonoured, and yet in their very dishonour are glorified. They are evil spoken of, and yet are justified; they are reviled, and bless; (2 Corinthians 4:12) they are insulted, and repay the insult with (honour); they do good, yet are punished as evildoers. When punished, they rejoice as if quickened into life; they are assailed by the Jews as foreigners, and are persecuted by the Greeks; yet those who hate them are unable to assign any reason for their hatred.
¹ Translated by Alexander Roberts and James Donaldson. From Ante-Nicene Fathers, Vol. 1. Edited by Alexander Roberts, James Donaldson, and A. Cleveland Coxe. (Buffalo, NY: Christian Literature Publishing Co., 1885.) Revised and edited for New Advent by Kevin Knight. <http://www.newadvent.org/fathers/0101.htm>. The date and author are unknown, yet generally ascribed to the second century AD.