In "The Cask of Amontillado," where in the story does Montresor tell his servants not to leave?
The quote to which you are referring occurs in the story right after Fortunato takes Montresor by the arm and insists on accompanying him home to his palazzo to sample the (nonexistent) Amontillado. Montresor is not shown giving explicit orders to his servants not to leave. Rather, he explains that he has already given these orders before he and Fortunato ever arrive. This is covered in one full paragraph shown below, and nowhere else.
There were no attendants at home; they had absconded to make merry in honour of the time. I had told them that I should not return until the morning, and had given them explicit orders not to stir from the house.These orders were sufficient, I well knew, to insure their immediate disappearance, one and all, as soon as my back was turned.
This passage is intended to show several things. One is that Montresor has no family. He may have had a wife and even children at one time, but now he is all alone in the world. Not all household servants would behave like Montresor's. The fact that they disobey him, and also the fact that he knew they would disobey him, shows that he is a poor man who cannot afford to hire first-class professional servants. Montresor obviously lives from hand to mouth. He appears to be a dealer in one-of-a-kind luxury items, such as oil paintings, antique furniture, gemmary (jewelry), and gourmet wines--anything where he can make a small profit and survive. No doubt he is not always able to pay his servants but can only provide food and shelter. They do not respect him, and they do pretty much as they please.
In the short story "The Cask of Amontillado" by Edgar Allan Poe, the story begins with Montresor explaining to the reader that revenge on Fortunato is foremost on his mind. The reader is only told that it is because he has borne too many insults at the hands of Fortunato. From that point on, Montresor devises a plot to lure his enemy down to the catacombs using the promise of wine as bait. The story takes place during carnival time in Italy.
To ensure that he will not be interrupted during his plot to kill Fortunato, Montresor tells his household servants to remain at the house, and by no means leave for any reason. Montresor knows well that his servants will do the exact opposite during carnival time as soon as Montresor turns his back:
"There were no attendants at home; they had absconded to make merry...I had given them explicit orders not to stir from the house...I well knew, to ensure their immediate disappearance...as soon as my back was turned." (Poe)
This, of course, shows how much forethought and manipulation went into Montresor's plan to take revenge on Fortunato.