Bonhoeffer in Life Together:
Finally, one extreme thing must be said. To forego self-conceit and to associate with the lowly means, in all soberness and without mincing the matter, to consider oneself the greatest of all sinners. This arouses all the resistance of the natural man, but also that of the self-confident Christian. It sounds like an exaggeration, like an untruth. Yet even Paul said of himself that he was the foremost of sinners (I Tim. 1:15); he said this specifically at the point where he was speaking of his service as an apostle. There can be no genuine acknowledgement of sin that does not lead to this extremity. If my sinfulness appears to me to be in any way smaller or less detestable in comparison with the sins of others, I am still not recognizing my sinfulness at all. My sin is of necessity the worst, the most grievous, the most reprehensible. Brotherly love will find any number of extenuations for the sins of others; only for my sin is there no apology whatsoever. Therefore my sin is the worst. He who would serve his brother in the fellowship must sink all the way down to these depths of humility. How can I possibly serve another person in unfeigned humility if I seriously regard his sinfulness as worse than my own? Would I not be putting myself above him; could I have any hope for him? Such service would be hypocritical. “Never think that thou hast made any progress till thou look upon thyself as inferior to all” (Thomas a Kempis).