Clarify Danforth's statement in Arthur Miller's The Crucible that "the entire contention of the state in these trials is that the voice of Heaven is speaking through the children."
The statement to which you refer is spoken in act three of The Crucible by Arthur Miller. Giles Corey, Francis Nurse, and John Proctor have all come to court to offer evidence that the girls are lying. The men's wives have all been imprisoned, and Proctor has convinced (coerced?) Mary Warren to come and tell the court the truth.
They finally get to talk to Danforth, and Proctor eventually gets to make his big announcement: the girls are lying and Mary Warren, one of those girls, has come to testify to that truth. Parris, of course, is immediately frightened and outraged (because he knows Proctor is right).
Parris: They’ve come to overthrow the court, sir! This man is--
Danforth: I pray you, Mr, Parris. Do you know, Mr. Proctor, that the entire contention of the state in these trials is that the voice of Heaven is speaking through the children?
Proctor: I know that, sir.
What Danforth is reminding the accuser (Proctor) of is that this is a very, very significant accusation. Until now, the court has had no reason to doubt the girls' truthfulness, assuming that they have been representing God (the voice of Heaven) as they call out true witches. If their accusations are shown to be lies, people who have died and are in prison have been wrongly convicted--and Danforth will have to live with that.
It is a weighty matter to consider because the consequences are life and death. This line is the beginning of Danforth's serious, pointed, and intimidating (to Mary, anyway) questioning to discover the truth. Things do not go well for Proctor or Mary, but at least the truth was spoken aloud, in court, and causes some to doubt. In fact, Reverend Hale quits the court at the end of this questioning because he, unlike Danforth, is willing to recognize and admit the truth.