Old Heraclitus is right -- he is a buddha -- he is right when he says you cannot step twice in the same river. No buddha is ever the same again; not even for two consecutive moments is he the same. He moves with life, he is a river, he is not stagnant. He has uniqueness, originality. He speaks, not authoritatively, but on his own authority.
Remember the difference. The person who speaks authoritatively derives his authority from somewhere else -- from the Vedas, from The Bible, from the Koran, from the tradition, from the state, from the church. The man who speaks on his own authority derives his authority from nowhere. It is his own experience -- and experience is self- evident, self-validating.