This is a trustworthy saying, and everyone should accept it: “[The] King, Jesus, came into the world to save sinners”—and I am the worst of them all. (The Apostle Paul, 1 Timothy 1:15, NLT)
One extreme statement must still be made, without any platitudes, and in all soberness. Not considering oneself wise, but associating with the lowly, means considering oneself the worst of sinners. This arouses total opposition not only from those who live at the level of nature, but also from Christians who are self-aware. It sounds like an exaggeration, an untruth. Yet even Paul said of himself that he was the foremost, i.e., the worst of sinners (1 Tim. 1:15).
He said this at the very place in Scripture where he was speaking of his ministry as an apostle. There can be no genuine knowledge of sin that does not lead me down to this depth. If my sin appears to me to be in any way smaller or less reprehensible in comparison with the sins of others, then I am not yet recognizing my sin at all.
My sin is of necessity the worst, the most serious, the most objectionable.
Christian love will find any number of excuses for the sins of others; only for my sin is there no excuse whatsoever. That is why my sin is the worst. Those who would serve others in the community must descend all the way down to this depth of humility. How could I possibly serve other persons in unfeigned humility if their sins appear to me to be seriously worse than my own? If I am to have any hope for them, then I must not raise myself above them.
Such service would be a sham.
(Dietrich Bonhoeffer, from Life Together, pp. 97-98, paragraphing mine)