Three of Rev. Dr. King's speeches can be found in the Free Music Archive under Creative Commons licenses, including "I Have A Dream," which is always worth hearing in its entirety.
The other two speeches are from the last few months of his life. One is from an anti-war demonstration for imprisoned activists (including Joan Baez). The other features a six-minute introduction from acclaimed writer James Baldwin.
https://freemusicarchive.org/music/Martin_Luther_King/The_Speeches
