Reverend Hale's passionate plea to Elizabeth, John's wife, encapsulates his entire argument. When he confronts her, he tells her that she should not misplace her duty and loyalty and believe that she is doing right. He states that he has made the same mistake and now has the blood of many innocents on his hands. He urges her to not cling to faith when it results in unnecessary bloodshed.
Furthermore, he contends that it is the law which is mistaken for it leads others to sacrifice. Hale insists that life is God's greatest gift and that no lofty principle can justify its taking. He pleads with her to ask John to confess even if it's a lie. She should not doubt God's judgment in this matter for it may be that God damns a liar less than one who gives away his life for pride. He urges her to talk to her husband because he believes that she is the only one to whom John will listen.
The Reverend's belief arises from the fact that he has lost faith in the court and its proceedings. He left in a huff at the end of Act three. At the time, he condemned what was happening and refused to be party to the court's judgment. Also, the Reverend feels burdened with guilt for having been involved in the incarceration and death of—what he now recognizes as—innocent victims of the girls' malice.
He later returns in the hope that his counsel with the condemned will help them confess and thus save them from execution. He is desperate to convince John because he believes that a confession from him will encourage others, such as Rebecca Nurse, to do the same. It is tragic that his good intentions fail since John, in the end, tears up his confession to save his name and retain the little integrity he still has.
John later refuses to implicate others when Judge Danforth asks him to do so. He angrily states:
Proctor: I speak my own sins; I cannot judge another. Crying out, with hatred: I have no tongue for it.
He is saying that he cannot speak for others. He can only confess to his transgressions and can't comment on what others did. He is clearly suggesting that the court cannot use him to testify against other accused and, in the process, condemn them.
In Act 4 of The Crucible, Reverend Hale returns to the court to persuade those who were falsely accused to confess to witchcraft so that they will not give their lives for something that they have not done -- this is evident when he says, "There is blood on my head. Can you not see the blood on my head?"
Hale's argument favoring John's confession is along the same lines as this. At this point, Hale realizes that Proctor is not a witch, has never practiced witchcraft and is a product of the mass hysteria that has overtaken Salem. Hale wants Proctor to confess because he knows that he is telling the truth and that the girls were total liars.
Furthermore, Proctor states, "I speak my own sins; I cannot judge another. I have no tongue for it," in Act 4 after he confesses to witchcraft. The judges ask him who else he has seen with the devil. Because John has committed the sin of adultery, he does not think that he can "judge another" -- that is what Proctor does not have the tongue for.