Which tv series coined the phrase the tribe has spoken?

Jeff Probst notes his mind came up blank, and it was actually producer Mark Burnett who came up with “the tribe has spoken,” but it was somewhat of an accident. Burnett told Probst, “Jeff, I don't know what to say, the tribe has spoken, that's just how it goes.”  

But in direct answer to your question, it was 'Survivor'

Hope this helps :)

Jeff Probst noticed his psyche came up clear, and it was really maker Mark Burnett who concocted the clan has spoken, however it was fairly a mishap.

Explanation:

Burnett told Probst, Jeff, I don't have the foggiest idea what to state, the clan has spoken, that is exactly how it goes.The Tribe Has Spoken: The Story Behind Survivor's Iconic Catchphrase.

So once I had strolled through [the first] Tribal Council and saw there was this light. I don't have the foggiest idea what to let you know, Jeff, the clan has spoken and that is the manner in which it goes.