On April 3, 1968, Dr. Martin Luther King Jr. spoke in support of a strike of sanitation workers in Memphis, Tennessee. The speech he gave, with biblical imagery and references, especially to the Israelites, their escape from slavery, and what their leader, Moses, was allowed to glimpse before his death,  has since become known as the Mountaintop speech. 

Video of the speech can be found on Youtube. The brief audio clips used here came from the internet archive.

https://archive.org/details/IHaveBeenToTheMountaintopFullSpeech

In the podcast audio, it might not be quite as clear as intended that "John Brown's Body" being referenced was a marching song of the Union army during the American Civil War. John Brown's raid on Harper's Ferry, which led to John Brown's trial and execution, occurred just a year before the election of Abraham Lincoln as president. 

https://en.wikipedia.org/wiki/John_Brown%27s_Body