From Dr. King’s last message:

We need all of you. And you know what’s beautiful to me is to see all of these ministers of the Gospel. It’s a marvelous picture. Who is it that is supposed to articulate the longings and aspirations of the people more than the preacher? Somehow the preacher must have a kind of fire shut up in his bones. And whenever injustice is around he has to tell it. Somehow the preacher must be an Amos, and saith, “When God speaks who can but prophesy?” Again with Amos, “Let justice roll down like waters and righteousness like a mighty stream.” Somehow the preacher must say with Jesus, “The Spirit of the Lord is upon me, because he hath anointed me,” and he’s anointed me to deal with the problems of the poor.”

Full text of his last message HERE. It also has the audio. It is a moving message to hear.