Martin Luther King on the day of his speech in front of the Lincoln Memorial announced to the whole country that we need to unite as a country in whole. Not blacks with blacks and white with whites, we need to be together as a whole. So as one of the literary devices he used he said “Go back to Mississippi, Go back to Louisiana” etc., as in freedom won’t be coming out as fast as they hoped and might not be even getting it.
MLK also used “So let freedom ring” as another literary device. So let freedom ring means wait