In The Crucible, the last line in the play spoken by Elizabeth Proctor is,

He have his goodness now, God forbid I take it from him.

What Elizabeth means is that her husband, John Proctor, has finally achieved redemption, and she will not take that away from him by asking him to confess to practicing witchcraft in order to save his life. The irony within the play is that by falsely confessing to witchcraft and then repenting, Proctor would avert a death sentence even though such a confession would be a lie. He did not engage in any practices of witchcraft.

He engaged in adultery with Abigail, which ultimately led to Abigail’s accusation of witchcraft against Elizabeth Proctor. John confesses to his adultery in order to save Elizabeth, thus redeeming himself in her eyes and in his own. The irony is that through this confession of his real misconduct, he faces a much harsher penalty than if he had lied and confessed to a different but false misconduct.

Through much of the play, Proctor has not wanted to embarrass himself and soil his good name by acknowledging his act of adultery. During the period of the Salem Witch trials, adultery was viewed as a sin against G-d, as well as an infraction of marital vows and an insult to one’s spouse. John’s confession is a relief to him because he has reclaimed his sense of honesty by telling the truth. Elizabeth does not want to take that away from him even though it means that he will be put to death. He will die as a good man.

Elizabeth Proctor speaks these words in response to an urgent request from Reverend Hale, who wants her to intercede with John and try to persuade him to give Deputy Governor Danforth the confession of witchcraft he demands.

But even though John's on his way to the gallows, Elizabeth refuses. This is because she knows that, in refusing to lie in confessing to witchcraft, John has finally attained a level of redemptive goodness that she has no right to take from him.

For the first time since John's affair with Abigail Williams came to light, Elizabeth now feels that she can trust and forgive her husband. It would be all too easy to follow Hale's desperate entreaties and try to get John to go along with what Danforth wants.

But she chooses not to do so because she trusts her husband, something that wasn't the case earlier in the play. If Elizabeth were to intervene, that would in some respects take the goodness away from John that he's earned through his decision not to confess and leave his children with a legacy of shame.

Although Elizabeth loves her husband and doesn't want to see him go to the gallows, she's not prepared to take away the goodness that he's finally achieved and the legacy it will pass on to his children and successive generations of Proctors.

Elizabeth utters this phrase at the very end of The Crucible, and it is very significant because it is the reason that she gives for not stepping in and pleading for John to not confess in order to save his life.  She is standing there, watching her own husband go to the gallows to hang, and doesn't beg for him to reconsider; instead, she says that he finally "has his goodness," and that she wouldn't dare interfere with that.

What Elizabeth means is that for the first time in a long time, John actually felt like he was a worthy, righteous, brave man.  He had spent the last long while feeling guilty over his affair, feeling bitter and upset at himself, feeling unworthy to be in the presence of more pious people, and feeling conflicted about his faith, minister, marriage and goodness.  He didn't like himself very much.  In fact, in his conversation with Elizabeth before this moment in the play, he confesses how he "cannot mount the gibbet like a saint...I am no good man."  He has no confidence in himself; he feels that if he stands all self-righteously up at the noose, touting his honesty before the world, that it would be a hypocrisy because he is not a good person. He has lied, he has committed great sins, and to go to the noose pretending that honesty is part of who he is, then he is fooling no one.  He feels intimidated at the prospect of going up there with the likes of Rebecca Nurse, renowned for her piety.

However, by the end of the act, John has made up with his wife, been forgiven by her for the adultery, and stood his ground on the issue of not confessing to a crime he didn't commit.  He refuses to confess and have his boys see his name on a list of "witches."  He refuses to leave them the legacy of a weak liar.  And the very act of standing his ground and deciding not to confess at the cost of his life is what, in the end, convinces him that he does have some goodness in him.  As he tears the confession he states,  "I do think I see a shred of goodness in John Proctor," and for the first time, is at peace with his life, his sins, and his past.  He is at peace.  That is what Elizabeth means--he is finally at peace with himself.  If she intervenes and forces him to confess, he won't have that anymore.  She respects his self-dignity more than her own selfish desires for him to live.  I hope that helped clear it up a bit; good luck!