The Pardoner is so morally corrupt and blatantly hypocritical, it is safe to say he should not be preaching about anything to anyone! Certainly it would not be appropriate for him to preach a sermon against greed since he is both consumed with greed and quite proud of his effectiveness in separating poor peasants from the few coins they might possess. The Pardoner abuses his position in the Church and uses his powers of persuasion to line his own pockets:
On one short day, in money down, he drew
More than the parson in a month or two,
And by his flatteries and prevarication
Made monkeys of the priest and congregation.
His defining character trait--this unlimited avarice--is shown first in Chaucer's "Prologue." When we first see the Pardoner, he rides with his wallet in his lap, "Brimful of pardons come from Rome all hot." In other words, he's ready for business. The Pardoner peddles phony religious relics, as well as pardons, to the unsuspecting faithful. Among his many talents, the Pardoner also is an excellent speaker in any church service. Not surprisingly, his strong suit is singing the Offertory prior to taking up a collection from the congregation.