Commentaries:
The first person who is named a prophet is Abraham. This occurrs when Abimelech is being instructed by God regarding Sarah, that he is to return her to Abraham.
However, Abraham is chronologically not the first person the Bible shows prophesying. That would be Enoch. It does not report on this until the book of Jude: "And Enoch also, the seventh from Adam, prophesied of these, saying, 'Behold, the Lord comes with ten thousands of his saints'" (Jude 1:14). Here Enoch, before the Flood, prophesies of the return of Jesus Christ with the saints.
John W. Ritenbaugh
Prophets and Prophecy (Part One)