I am writing an essay for the Crucible, and I need help with selecting evidence for how Reverend Hale changes throughout the novel. I need four pieces of evidence showing his change.

When Reverend Hale first arrives in Salem, he says, rather importantly, that the many books he brings are "weighted with authority." He tells those gathered in Betty's room about the books:

Here is all the invisible world, caught, defined, and calculated.  In these books the Devil stands stripped of all his brute disguises.  Here are all your familiar spirits—your incubi and succubi; our witches that go by land, by air, and by sea; your wizards of the night and of the day.  Have no fear now—we shall find him out if he has come among us, and I mean to crush him utterly if he has shown his face!

Hale is tremendously confident, even perhaps somewhat arrogant, in his his own ability and power.  The pride that he takes in his education and discernment is clear, and he seems to have no fear that he might be up against an opponent that could best him.  While others quail before and fear the unknown, Hale seems to feel that there is no such unknown—he believes that his books contain everything he needs to know—so he has no fear.
In act two, when Francis Nurse arrives at the Proctors' home to tell John Proctor that Rebecca, Francis Nurse's wife, has been arrested, Hale says,

Let you rest upon the justice of the court; the court will send her home, I know it. 

He is clearly quite confident in the court's justice, and he is sure that there can be no corruption tolerated (or initiated) by Deputy Governor Danforth.  He is incredibly naive.  Further, he tells Proctor, in regard to Rebecca,

Man, remember, until an hour before the Devil fell, God thought him beautiful in heaven.

Hale is confident in the idea that there is a "misty plot afoot" in Salem, and he does not doubt the accusers' truthfulness or the honesty of the court.  Rather, he doubts the integrity of individuals who have been counted as honest and good for their entire lives.  He will not listen to Proctor, Giles Corey, or Francis Nurse, and he essentially sits by while their wives are carted off to jail.  This is why Proctor calls him "Pontius Pilate": the man seems to wash his hands, figuratively, of the blame being placed on these obviously innocent individuals.  His ultimate faith in the court trumps all else.
In act four, however, Hale returns (he quit the court at the end of act three), saying, 

I come to do the Devil's work.  I come to counsel Christians they should belie themselves.  There is blood on my head!  Can you not see the blood on my head!!

Hale now understands that the court is corrupt, that innocent people are being hanged for crimes they did not commit, and that the magistrates are more concerned about retaining their authority than the lives of the people who are scheduled to hang.  He is trying to get those people who have been convicted to confess and lie in order to save their own lives.  His confidence is gone, and he realizes the responsibility he bears in what has occurred. Hale tells Elizabeth Proctor, that if John, her husband, is executed, Hale will consider himself John's murderer.  Hale feels personally responsible for the hangings because he had assured these people that the court would find out the guilty parties and let the innocent go; this is not what happened.  Hale also tells Elizabeth Proctor,

Let you not mistake your duty as I mistook my own.  I came into this village like a bridegroom to his beloved, bearing gifts of high religion; the very crowns of holy law I brought, and what I touched with my bright confidence, it died; and where I turned the eye of my great faith, blood flowed up.

All of Hale's earlier confidence is gone.  He is no longer proudly arrogant concerning his powers of discernment, his education, or his books.  He feels now that he was totally mistaken in his "bright confidence" and recognizes the part he played in these deaths.