What "you must take" in both cases is somebody's creative writing: Hawthorne's book of short stories and the narrator's unexpected burst into verse.
HAWTHORNE AND HIS MOSSES
Take these raspberries, and then I will give you some moss."—"Moss!" said I—"Yes, and you must take it to the barn with you, and good-bye to 'Dwight.'"
--The Literary World Volume 7 (August 17, 1850) page 125.
SCENES BEYOND THE WESTERN BORDER
How dreary must be a great Commodore ,
Alone in the cabin of a seventy-four.
Be not alarmed ! I make a rhyme but once a year ; the idea came in that shape , and you must take it as it comes .