Throughout "The Man That Corrupted Hadleyburg," Twain's characters mutter the Hadleyburg motto as “lead us not into temptation." By the end of the story, Twain playfully reverses the meaning of the motto by removing just one word: “lead us into temptation.” The original phrase is a biblical allusion, to the "Lord's Prayer," from Matthew 6:13: “And lead us not into temptation, but deliver us from evil: for thine is the kingdom, and the power, and the glory, for ever.”
The phrase, and the rabid denial of temptation, embodies the sentiment of Hadleyburg’s citizens at the outset of the story: that all temptation is bad, and all temptation should be avoided. This attitude brings about the downfall of the town's nineteen citizens, as they are utterly unprepared to deal with the feelings of extreme greed they feel the moment they are faced by an actual temptation: the moment the gold arrives in Hadleyburg, the Nineteen debase themselves in their dishonest attempts to claim it as their own.
The revised motto reflects the more nuanced attitude toward temptation achieved by Hadleyburg by the end of the story. With the Nineteen disgraced, the Richards couple dead from the stress of the ordeal, and the insularity of the town shattered by the notoriety of the situation, the remaining citizens understand the nature of the real world outside of Hadleyburg's "honest" bubble: inevitably, they will be tempted, but only through the experience of actual temptation can they learn to overcome it with real virtue.
In Section 1, Mary Richards laments that her husband, Edward, was not the man who performed the favor that earned the mysterious sack of gold as a reward. As she remarks on the "fortune" that the gold represents for whoever had been kind enough to perform this favor, she makes an idiomatic allusion:
Mrs. Richards sat down, gently quivering with excitement, and was soon lost in thinkings—after this pattern: “What a strange thing it is!...And what a fortune for that kind man who set his bread afloat on the waters!...If it had only been my husband that did it!—for we are so poor, so old and so poor!
To “set bread afloat on the waters" is an idiom that means to do a deed without expectation of a reward. This idiom is itself an allusion to a passage in Ecclesiastes, a section of the Hebrew Bible and the Christian Old Testament traditionally attributed to King Solomon of Israel: “cast thy bread upon the waters: for thou shalt find it after many days.”
Though Twain may or may not have selected such an idiom because of its biblical implications, its inclusion in "The Man That Corrupted Hadleyburg" nonetheless underscores the significance of notions of Christian virtue to the citizens of Hadleyburg (and, more generally, to the many rural communities in America that Twain made the subject of much of his writing). The central, ironic conflict in the story satirizes this sense of morality: each citizen is vain to the point of pretending to have been virtuous enough to have done a good deed.
From the very beginning of Twain's story, it is clear that the supposedly virtuous citizens of Hadleyburg have a particular disposition toward vindictiveness and cruelty. As Edward Richards discusses his history with Reverend Burgess in Section 1, he reveals some of this darker side through an allusion to an attempted punishment of Burgess for an unspecified misdeed:
"I can explain it. It's another confession. When the thing was new and hot, and the town made a plan to ride him on a rail, my conscience hurt me so that I couldn't stand it, and I went privately and gave him notice, and he got out of the town and staid out till it was safe to come back."
"The Man That Corrupted Hadleyburg" contains no shortage of references to the various quirks of small-town culture in rural, 19th-century America. This passage, however, contains a particularly brutal one: the plan to "ride [Burgess] on a rail" that Edward Richards mentions is an allusion to a real tactic for public shaming in the 18th and 19th centuries in which an offender was made to straddle a fence-rail and then carried around town in a cruel parade (or, otherwise, simply carried to the edge of town and left there for presumptive self-exile).
This passage presents a subtler example of Twain's satire: Richards's mention of this punishment is a passing mention of a historical conflict in Hadleyburg, yet the very fact that such a punishment was on the table speaks volumes for the Hadleyburg citizens' propensity towards merciless revenge on (and shaming of) their peers—a trait that will be on full display as the town dissolves into chaos following the arrival of the stranger's "gold."
In Section 3, the stranger (and the many, many other people who have long awaited Hadleyburg's downfall) finally begin to get their revenge on the town for its excruciating sense of superiority and brutal treatment of outsiders: eighteen of the nineteen prominent citizens of Hadleyburg have revealed themselves to be liars and frauds by all concurrently claiming to be the rightful heir to the mysterious sack of gold. The joy of the crowd, witness to this spectacular fall from grace, only grows as Reverend Burgess reveals the claim made by each successive member of the Nineteen. When Burgess reveals Mr. Pinkerton's claim to the bag, only the third to be read, Twain uses an idiomatic expression that comes from Shakespeare's Hamlet to express the crowd's delight:
The pandemonium of delight which turned itself loose was of a sort to make the judicious weep. Those whose withers were unwrung laughed until tears ran down[.]
To have one's "withers" be "unwrung" means to be unaffected or unafflicted. Twain paraphrases the line from Hamlet, Act 3, Scene 2, in which Hamlet declares to Claudius: “Let the galled jade wince, our withers are unwrung.” Literally, the idiom refers to the wear-and-tear on a horse's back: a "galled jade" is a sore, worn out horse, and the "withers" are a part of a horse's back right below the neck. Unlike a sore horse, Hamlet means to say, he feels fine.
Accordingly, in "The Man That Corrupted Hadleyburg," those whose withers are unwrung are those outsiders and townsfolk in the crowd who have been unaffected by the erupting scandal of the false claims to the gold (in other words, everyone in the crowd save the Nineteen)—and they rejoice accordingly.