Funny story: That's a line from Shakespeare's Julius Caesar.
It's uttered by Mark Antony, as he forms a plan to engulf the Roman Empire in a brutal civil war. The picture he paints of this war is the stuff of nightmares ("Blood and destruction shall be so in use / And dreadful objects so familiar / That mothers shall but smile when they behold / Their infants quartered with the hands of war / All pity choked with custom of fell deeds").
He starts this civil war by stirring up the crowd at Caesar's funeral with hyperbolic language, inciting a riot that ends with vandalism, arson, and the murder of at least one man by literally ripping him to pieces.
His response as the rioters exit, with the knowledge and expectation they will do such things, is, "Now let it work. Mischief, thou art afoot. / Take thou what course thou wilt!"
He then takes control of the Empire (along with two prominently-named but easily-controlled men) and proceeds to rule it exactly the way it was feared Caesar would have, as a tyrant.
So...if you're a Trump supporter, I wouldn't use that quote. Just sayin'.
