Hi, you've asked an incomplete question. However, I provided a specific line that fits into the central irony of "The Pardoner's Prologue."
Explanation:
Remember, in English literature, Irony refers to a literary device that uses words/expressions whose intended meaning is actually the opposite of the literal meaning of the word. So in a sense what one expects to see/read; isn't always presented that way.
For example, notice this line from the story,
"The men found what they were looking for. The two men toasted the successful murder of their friend with a bottle of wine that the friend brought for them...."
Here we notice an unusual activity from the men; ideally, no one would expect those responsible for the murder of someone to make a toast to the individual they killed using a bottle of wine provided by that person, indeed it is an irony.