Chaucer's "The Pardoner's Tale" is particularly ironic.
Irony, as Dr. L. Kip Wheeler puts it, is:
...saying one thing and meaning another.
A great deal of the information in Chaucer's Prologue to the Canterbury Tales is garnered by reading between the lines, as Chaucer describes his larger-than-life characters with a "twinkle in his eye," and tongue in cheek. A student of human nature, Chaucer saw beyond appearance to the heart of the individual. And although the structure of his tale is based upon a pilgrimage to the Canterbury Cathedral, where Thomas à Becket was martyred by King Henry II's men-at-arms, many of those who Chaucer "travels with" are anything but holy in behavior or mindset. However, Chaucer allows the audience to judge his characters while he, acting like a member of the pilgrimage, reports what he sees.
The Pardoner's job is to "sell" indulgences ("forgiveness") to those who have sinned. (Chaucer was a critic of this and other aspects of the Church of his time.) The Pardoner is supposed to be a member of the "clergy." This means he was employed to serve the public in a religious way, which would have entailed giving up his worldly possessions, putting others before himself, dressing in plain clothing without adornment, and devoting his life to the good of others.
Ironically, the Pardoner is stylishly-presented, concerned with his good looks, carries "hot" (or stolen) pardons from Rome, and has fake "souvenirs," such as a pillowcase he presents as the veil of the Virgin Mary, as well as fragments of the sail of St. Peter, used to impress unsophisticated country "clergymen."
The last part of this ironic portrait of a man of the cloth who is more interested in benefitting himself than the congregation he serves, is the pardoner's songs offered up as if in praise of God, while in truth, the better he sings (he knows), the more money will be in the offering plate he passes around—for him. That which seems to indicate what a dedicated man of God he is, shows more how dedicated he is to filling his own pockets.