Epistle to Diognetus

To sum up all in one word— what the soul is in the body, Christians are in the world. The soul is dispersed through all the members of the body, and Christians are scattered through all the cities of the world. The soul dwells in the body, yet is not of the body; and Christians dwell in the world, yet are not of the world. The invisible soul is guarded by the visible body, and Christians are known indeed to be in the world, but their godliness remains invisible. The flesh hates the soul, and wars against it, though itself suffering no injury, because it is prevented from enjoying pleasures; the world also hates the Christians, though in nowise injured, because they abjure pleasures.

The soul loves the flesh that hates it, and [loves also] the members; Christians likewise love those that hate them. The soul is imprisoned in the body, yet preserves that very body; and Christians are confined in the world as in a prison, and yet they are the preservers of the world. The immortal soul dwells in a mortal tabernacle; and Christians dwell as sojourners in corruptible [bodies], looking for an incorruptible dwelling in the heavens. The soul, when but ill-provided with food and drink, becomes better; in like manner, the Christians, though subjected day by day to punishment, increase the more in number. God has assigned them this illustrious position, which it were unlawful for them to forsake.