voice in the wilderness

noun2

1. •
   A person, publication, or other source of assertions that expresses an opinion, doctrine, or point of view which is ignored or rejected by almost all others; the actual utterance of an unpopular opinion, doctrine, or point of view.

   • A leader without committed followers is an unheard voice in the wilderness. — 1994
2. •
   (rare) An influential religious personage, especially one who makes prophetic utterances.

   • "I don't know," said Anne. "He gathers together a little flock of all denominations, who only care to hear the word." "Such a voice in the wilderness as often does good service," said Julius. — 1876