In Act III, what quotation did Proctor use to help Mary Warren remain brave in The Crucible?
In Act 3, John Proctor does, in fact, twice refer to the same scripture in his wish to encourage Mary Warren and to strengthen her resolve. When he first speaks to her in court before taking out her deposition, he tells her:
Remember the angel, what he say to the boy. Hold to it, now; there is your rock.
Proctor is alluding to the book of Tobit, one of the books of the Apocrypha, which is seen by some as part of the Bible, while others do not acknowledge it. The story relates the experience of Tobias, the son of a deeply religious man (Tobit) who fell in love with Sara, a woman plagued by a demon that killed each of her seven previous husbands.
Tobit managed to defeat the demon on his wedding night with the help of the archangel Raphael. The angel had advised Tobias to "Do that which is good, and no harm will come to thee." Proctor later refers to the same verse but is unable to complete the line because of Abigail's intervention.
In the first instance, Proctor wants Mary to be strong, and he appeals to not only her reason but also her religious conviction. He is advising her to be like Tobias, implying that by doing good, she will have divine protection, and no harm will befall her. Just as in Tobias's situation, she will be able to overcome the demons plaguing Salem.
Proctor is indirectly referring to Abigail and the other girls who have managed to deceive the court and many others by lying about the presence of witches and the practice of witchcraft. Their testimony has led to many being accused and incarcerated, including Proctor's wife, Elizabeth. Mary is there to prove, once and for all, that what she, Abigail, and the other girls have been doing was all a hoax. Proctor hopes that her testimony will finally convince the court of his wife's and others' innocence, which will lead to their release.
When Mary Warren starts her testimony, her credibility is questioned when she is asked to faint as easily as she claims they have been able to do. Mary cannot, for she does not "have a sense of it." At this point, Abigail suddenly puts on an act stating that she is feeling a "cold wind." Proctor desperately grabs her and cries out that she is a whore. His actions lead to Elizabeth being called forth to testify why she dismissed Abigail. Elizabeth fails to mention her real suspicion and Proctor is left helpless.
Abigail senses an advantage, and she puts on an amazingly convincing act in which she claims that Mary's spirit is threatening her in the form of a yellow bird. The other girls soon follow her lead, and Mary Warren is eventually completely distraught and overwhelmed. Proctor, realizing that everything is falling apart, again calls on Mary saying:
Mary, remember the angel Raphael—do that which is good and—
He does not get a chance to complete the quote, because Abigail interjects and cries out that the supposed bird is preparing to swoop down and harm her. His appeal is ineffective and Mary, in absolute despair, turns against him and accuses him of doing the devil's work and trying to force her to join him and sign the Devil's book. The result is that Proctor is arrested and taken to jail.
When Mary Warren comes to the court to tell the truth, that Abigail and the other girls are lying when they accuse people of witchcraft and acting when they appear to faint and freeze, Abigail turns on her and prepares to accuse Mary of witchcraft. She insists that she sees Mary's spirit as a yellow bird who threatens to tear her face, and she claims that Mary sends a cold wind. Then, when the other girls join her, Mary's resolve begins to weaken. Proctor tries to bolster her spirits by saying, "Mary, remember the angel Raphael -- do that which is good and--," but he is cut off by more of Abigail's histrionics. The full line would have read, "Do that which is good and no harm will come to thee." However, Proctor really cannot promise this, and Mary knows it. Many people have already been convicted of witchcraft on the basis of the girls' similar accusations, and those people sit in Salem jail, getting ready to hang -- they tried to do what was good and harm has most certainly come to them.
The quote from Act III that John Proctor used to help Mary Warren remain brave was:
"Now, remember the angel Raphael and what he said to the boy Tobias...Do that which is good, and no harm shall come to thee."