Which phrase in martin luther king, jr.’s "i have a dream" speech is an example of an allusion?

 "My country 'tis of thee, sweet land of liberty, of thee I sing.
Land where my fathers died, land of the Pilgrim's pride,
From every mountainside, let freedom ring!"
Finally, King appeals to his audience's sense of nationalism, calling upon them to achieve the founding ideals of the nation: liberty and freedom.

Bbecause the jim crow laws were made to make voting difficult for african americans