Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
Arnoldists were a Proto-ProtestantChristian movement in the 12th century, named after Arnold of Brescia, an advocate of ecclesiastical reform who criticized the great wealth and possessions of the Roman Catholic Church, while preaching against infant baptism and transubstantiation. His disciples were also called "Publicans" or "Poplecans", a name probably deriving from Paulicians (the term "Publicani" would be generally used for any heretic, even a political traitor, through Europe).
Arnoldists' tenets would later be addressed by Bonacursus of Milan, c. 1190, in his Manifestatio haeresis Catharorum, which refuted Arnoldist apostolic poverty and the incapacity of sinful priests to administer the sacraments.