In her 1978 book, Illness as Metaphor, Susan Sontag warns that the use of illness as a metaphor can cause us to regard physical illness as a mark of despair and inhumanity. More recent theological consideration of disease and disability by figures such as Devan Stahl and Louise J. Lawrence have raised similar concerns about careless theological or pastoral use of disease as a metaphor for sin. These concerns should spark careful consideration of how Biblical and traditional language of sin as disease might be responsibly retrieved. In this paper, I argue that Gregory Nazianzen’s Oration 14, “On Love for the Poor,” is an important model for speaking of sin as disease in a way that reflects the seriousness of sin without demeaning the ill. Gregory’s rhetoric troubles direct connections between physical health and sinfulness, describing sin as a spiritual disease in order to flip the self-perception of the uncaring rich upon its head. After speaking at length about the plight of the poor and the diseased, Gregory turns to the rich and healthy. In a move designed to arrest and challenge his hearers, he proclaims that the ones in the direst need of healing are those who are confident in their self-sufficiency and callous in their attitude towards the less fortunate. The callous rich suffer from a disease that is chosen and has eternal consequences, while the physically ill often surpass the rich in spiritual health. There is no necessary correlation between physical and spiritual health, though the fit and wealthy are often in more danger of believing in illusory self-sufficiency. The disease of the callous rich must be cured by reliance upon Christ, the wounded healer, and by exhibiting his compassion to the suffering. Gregory’s discussion of the sin that infects the rich as a form of spiritual disease provides several important lessons in speaking of sin as illness and helps to address concerns regarding over-identification between physical disease and sinfulness. First, Gregory carefully distinguishes between the culpability attached to (chosen) spiritual disease and the blamelessness attached to (unchosen) physical disease. Second, Gregory uses the image of sin as illness to relativize the distance between the physically healthy and ill, thus unsettling rather than entrenching judgements of worth based upon physical health. Third, Gregory describes sin as disease not merely to condemn his audience, but to call his audience to repentance and lives of compassion and service. Finally, Gregory refuses to see even spiritual disease as the final word, appealing to Christ as the one who offers healing to the spiritually sick. Gregory thus offers a positive model of how we might speak of sin as a serious spiritual illness while simultaneously affirming the value of those who suffer from physical illness. For Gregory, it is mutual love and care, rooted in the power and example of Christ, that is the true mark of spiritual health.