In the second century an unknown Christian wrote a letter to his pagan friend Diognetus to explain to him why Christians are different and how God has both delivered them from sin and brought them to eternal life through the death and resurrection of Jesus Christ, His Son.

The difference between Christians and the rest of mankind is not a matter of nationality, or language, or customs. Christians do not live apart in separate cities of their own, do not speak any special dialect, nor practice any eccentric way of life. The doctrine they profess is not the invention of busy human minds and brains, nor are they, like some, adherents of this or that school of human thought.  They pass their lives in whatever township – Greek or foreign – each man’s lot has determined; and conform to ordinary local usage in their clothing, diet, and other habits.

Nevertheless, the organization of their community does exhibit some features that are remarkable, and even surprising. For instance, though they are residents at home in their own countries, their behaviour there is more like that of transients; they take their full part as citizens, but they also submit to anything and everything as if they were aliens. For them, any foreign country is a motherland, and any motherland is a foreign country. Like other men, they marry and beget children, though they do not expose their infants. Any Christian is free to share his neighbour’s table, but never his marriage-bed. Though destiny has placed them here in the flesh, they do not live after the flesh; their days are passed on the earth, but their citizenship is above in the heavens.

They obey the prescribed laws, but in their own private lives they transcend the laws. They show love to all men – and all men persecute them. They are misunderstood and condemned; yet by suffering death they are quickened into life. They live in poverty, but enrich many; they are totally destitute, but possess an abundance of everything. They suffer dishonour, but that is their glory. They are defamed, but vindicated. They respond to abuse with blessing, and deference is their response to insult. For the good they do, they suffer punishment as evildoers; and under the strokes they rejoice like men given new life. They are assailed as heretics and harassed with persecutions; and yet of all their ill-wishers there is not one who can produce good grounds for his hostility.

Letter to Diognetus (2nd century)
1 Peter 2:9-12
John 17:6-18