"The Lord said to him, 'Who gave man his mouth? Who makes him deaf or mute? Who gives him sight or makes him blind? Is it not I, the Lord? Now go; I will help you speak and will teach you what to say'" (Ex. 4:11-12).
In Old Testament times there were usually only a few prophets on the whole earth at any one time. Sometimes prophets were contemporaries (Haggai and Zechariah, Isaiah and Jeremiah), but for the most part they operated in isolation as the lone mouthpiece of God.
They often were not incorporated into the daily religious life and traditions but stood apart, separated unto God.
No prophet exemplified this more than Elijah, who stood alone against King Ahab, the prophets of Baal, and the sins of a rebellious people. John the Baptist fits that mold as well—the man of God coming out of the wilderness to proclaim repentance because the Day of the Lord was imminent.
These prophets spoke with a clear and unmistakable, "Thus saith the Lord!" The authority of God's prophets was not limited to the general content or the main ideas of their message. Rather, they claimed repeatedly that their very words were the words that God had given them to deliver.
There was never a question about accurately discerning the genuine word from God. For the prophet, it was only a matter of whether he had the courage to deliver it.
Lord, if You call me to the ministry of prophecy, I recognize that I must only speak the words You place within my spirit. Give me the courage to deliver Your words—and just Your words, none of my own.