What is the literal meaning of this "cashing the check" metamor?

The phrase "cashing the check" goes back to Dr. Martin Luther king's "i have a dream" from his sentence he stated "in a sense we've come to our nation's capitol to cash a check" meaning they go all the way to the government to try and fight for rights of african americans

cashing the check initially means finally getting the rights of life. liberty, and the pursuit of happiness.

means to literally cash a check. It means you'll get cash in hand. You can walk away with the full amount of the payment, and you'll be able to spend that money immediately