On the last day of Pesach in every fourth and seventh year, a person would come to the Mikdash and do Vidui Maasaros. What is unique about the Mitzvah of Maaser that a person would make this declaration? We don't find such declarations by other Mitzvos.
Have a good Shabbos
Bonus found after doing the recording - Pashtus the language of Vudui found in Chazal here is a declaration, not a confession, and that is how Malbim explains it. However the Seforno translates it as a confession, and gives a pshat how there is a confession here, from the fact that we are giving it to Shevet Levi instead of the Bechorim, which was a result of our sins with the Eigel. Seems to me like a Shmuess that we are confessing for that today, and that are we maybe supposed to tap into those feelings of shame every time we do this vidui.