"The thousand injuries of Fortunato I had borne as I best could, but when he ventured upon insult I vowed revenge."
This is what Montresor said when Fortunato wronged him
Come down to the catacombs with me.
Montresor and Fortunato go down to the catacombs
Foreshadowing that Fortunato has attacked him which means he will be punished
No one attacks me without being punished.
Fortunato is sealed away and left to die by Montresor
This shows foreshadowing because in the beginning of the story the reader is told that Fortunato had attacked/wronged Montresor. Then later in the story Montresor says "No one attacks me without being punished.” This shows makes the reader know that Fortunato would be punished later.