What is the earliest makor for using money for “Kaparos” on Erev Yom Kippur?
Answer:
It appears to be a new custom.
See Mo’adim Uzmanim, Yom Kippur 52, who speaks of the “new custom” of using money in place of the traditional chickens.
Still it has become the popular custom today, even among benei torah.
Best wishes.
