forthspeaker

One who speaks forth or makes declaration; an announcer.

He was not a soothsayer or foreteller of events, but a forthspeaker of a message from Jehovah.

For example, Charles Kingsley's argument that God still sends prophets to guide man is obviously based upon this conception of the prophet as forthspeaker rather than foreteller.

A prophet.

[...] to the forthspeaker for God this book has the greatly enhanced value that it is by one who had learned what many historians have ignored [...]

In "Prophet from Highland Avenue: Agee's Visionary Journalism," Paul Ashdown discusses Agee as sage, as forthspeaker in his journalistic works and his film criticisms.