In Chapter XXIV of The Scarlet Letter, Nathaniel Hawthorne as narrator instructs his readers,
Among many morals which press upon us from the poor minister's miserable experience, we put only this into a sentence:—“Be true! Be true! Be true! Show freely to the world, if not your worst, yet some trait whereby the worst may be inferred!”
The sin which the Reverend Arthur Dimmesdale has kept secret within his heart has poisoned his body. Tortured by his guilt day after day, Dimmesdale becomes physically ill as he despises his hypocrisy and cowardliness in not admitting to his sin with Hester Prynne. Finally, when he can no longer live with the terrible weight of his sin of pride in believing that he can do God's work and his sin of adultery and irresponsibility to his daughter for which he cannot be forgiven until he acknowledges Pearl, he makes a public admission of his sins, standing on the scaffold with Hester and Pearl, saying to his congregation,
He bids you look again at Hester's scarlet letter! He tells you, that, with all its mysterious horror, it is but the shadow of what he bears on his own breast, and that even this, his own red stigma, is no more than the type of what has seared his inmost heart! Stand any here that question God's judgment on a sinner? Behold! Behold, a dreadful witness of it!”
It is also in her admission of sin and her acts of atonement that free Hester Prynne's soul. Hester bears the humiliation and scorn of the community, donating money that she earns to the community, aiding the ill and dying. After her years of charitable work, the community perceives Hester's letter to mean "Angel" rather than "Adulteress." Thus through her truthfulness, humility, and good works, Hester Pyrnne regains spiritual dignity.
In contrast to her, Hester's estranged husband, Roger Chillingworth, who has "violated the sacredness of the human heart" by surreptitiously probing into the heart of the Reverend Dimmesdale, finds his soul becoming blacker and blacker; in short, he becomes, by his own admission, "a fiend," who is mistaken for the "black man" who goes into the forest primeval.
And, little Pearl, the "airy sprite" who is the incarnation of Hester and Dimmesdale's sin, only becomes human when her father acknowledges her publicly. When Pearl kisses her father's lips, she becomes a person of her own, redeemed from the ostracism of sin:
A spell was broken. The great scene of grief, in which the wild infant bore a part, had developed all her sympathies; and as her tears fell upon her father's cheek, they were the pledge that she would grow up amid human joy and sorrow, nor for ever do battle with the world, but be a woman in it. Towards her mother, too, Pearl's errand as a messenger of anguish was all fulfilled.
Indeed, it is only the truth that sets free the souls of sinners. Hawthorne exhorts his readers to heed this message and to "be true!" and honestly admit to any wrongdoings in order that they may live a satisfying life without guilt.