What is the significance of Proctor speaking the Angel Raphael's words to Mary Warren: "Do that which is good and ho harm shall come to thee."

This is a great moment in the drama.  John Proctor is
trying to bolster an obviously weakened Mary Warren.  For a girl who is terrified of
betraying the "Queen Bee" of Abigail and the rest of her "Mean Girls," it makes sense
that Mary Warren's appearance in court is one of being weak and discombobulated at the
task in front of her.  Even Judge Danforth, who is not one for understanding, remarks
that "She's not hearty, I see" at the sight of Mary Warren.  Proctor's words at this
point of the angel Raphael are meant to comfort and guide Mary in a most difficult
time.  The words are meant to help Mary.

If they are
deconstructed, one can see the reason Miller employs their use.  The idea "doing good"
is something that has been so very lost in Salem at the time. Proctor's hope in using
them is to invoke some level of moral guidance in a setting where there is no moral
structure or guidance apparent or available.  Additionally, the idea of "doing good" and
"no harm will come to thee" is something that Mary starts out believing.  Yet, when
Abigail and the other girls gang up on her and torment her with exclusion and
intimidation, Mary capitulates and turns on Proctor in order to be with "the group." 
The idea that "no harm will come to thee" is in recognition of doing right by Abigail,
the individual who has the power in this scene.  Proctor's attempts to use the words in
the hopes of establishing morality and justice are in vain, just as his confession in
the hope of stopping the madness of the trial is
futile.

The final point in the use of the angel Raphael's
words is the very essence of defining "that which is good."  In the courtroom setting,
this becomes very difficult to decide for different people.  For instance, Hale tries to
protest the manner of the proceedings, but is silenced and simply takes it rather than
doing something more forceful about it.  By the end of the play, one has to wonder if
this represents "Do that which is good."  Elizabeth is tossed into the fire in the midst
of the court proceedings.  In her defense of her husband, she lies to try to save him. 
Seeing what awaits both she and her husband at the end of the play, one has to question
if what she did represented, "Do that which is good."  Finally, Giles Corey refuses to
name names and Francis' names on the petition becomes the source of new enquiries for
the court.  In this, one has to wonder what they thought in terms of if they did "that
which is good."  The entire court proceedings, where justice has been inverted for
personal gain, and the search for truth is illusory, help to establish a certain amount
of hollowness in the angel's words that Proctor turns to for comfort in a time of
distress.