This is an excerpt from The Epistle to Diognetus, one of the earliest pieces of Christian apologetic writing. While we are not sure of the author, it was probably written sometime in the 100's. For the sake of reference, Justin Martyr, the most well known apologist of the early church, lived roughly 100-165.
5 For Christians cannot be distinguished from the rest of the human race by country or language or customs. 2They do not live in cities of their own; they do not use a peculiar form of speech; they do not follow an eccentric manner of life. 3This doctrine of theirs has not been discovered by the ingenuity or deep thought of inquisitive men, nor do they put forward a merely human teaching, as some people do. 4Yet, although they live in Greek and barbarian cities alike, as each man's lot has been cast, and follow the customs of the country in clothing and food and other matters of daily living, at the same time they give proof of the remarkable and admittedly extraordinary constitution of their own commonwealth. 5They live in their own countries, but only as aliens. They have a share in everything as citizens, and endure everything as foreigners. Every foreign land is their fatherland, and yet for them every fatherland is a foreign land. 6They marry, like everyone else, and they beget children, but they do not cast out their offspring. 7They share their board with each other, but not their marriage bed. 8It is true that they are "in the flesh," but they do not live "according to the flesh." 9They busy themselves on earth, but their citizenship is in heaven. 10They obey the established laws, but in their own lives they go far beyond what the laws require. 11They love all men, and by all men are persecuted. 12They are unknown, and still they are condemned; they are put to death, and yet they are brought to life. 13They are poor, and yet they make many rich; they are completely destitute, and yet they enjoy complete abundance. 14They are dishonored, and in their very dishonor are glorified; they are defamed, and are vindicated. 15They are reviled, and yet they bless; when they are affronted, they still pay due respect. 16When they do good, they are punished as evildoers; undergoing punishment, they rejoice because they are brought to life.