Reverend Hale had been to Andover and witnessed the dissatisfaction of the court by the people who found the accusations of the "witches" there unfounded and unjust. Reverend Hale has seen the errors of his ways. He now believes that saving the lives of the condemned is more important than anything, even if one must lie to save one's life.
In Act IV, Scene 2, he says sarcastically to Danforth, (who asks, "Why have you returned here?"), "Why it is simple. I have come to do the Devil's work. I come to counsel Christians they belie themselves. (His sarcasm collapses.) There is blood on my head! Can you not see the blood on my head?"
Later, Hale says to Elizabeth: "Goody Proctor, I have gone this three months like the Lord into the wilderness. I have sought a Christian way, for damnation's doubled on a minister to counsel men to lie."
Hale advises Elizabeth, in light of his new position: "Beware, Goody Proctor -- cleave to no faith when faith brings blood. It is mistaken law that leads you to sacrifice... let him give his lie. Quail not before God's judgment in this, for it may well be God damns a liar less than he that throws his life away."
In Act 4, Danforth asks Hale if he has been preaching over in Andover in the past month because it is rumored there is rebellion in Andover, and Hale has just mentioned rebellion occuring in Salem. Hale replies that Andover has no need of him.
Hale has come back to the Salem prison to advise the condemned to 'confess' to witchcraft even though he knows they are not guilty. He is trying to save their lives. He feels responsible for their deaths, and is struggling to get them to confess so at least they will live. Hale knows at this point that the witchcraft trials have been a farce.