Shekalim 8 - Scooping the shekalim
All of the collected shekalim coins were deposited in a certain chamber in the Temple, and three times a year they would scoop the money from there, before each of the three holidays: Passover, Shavuot and Sukkot. These were also times designated for separating the tithe of the animals. These times (about two weeks before each holiday) were established by the Sages for a few reasons: these are normal times when the animals bear their young; so that the people had the meat to eat at pilgrimages, and so that they would not delay their offerings.
Scooping was performed with three boxes, numbered aleph-beit-gimel, and some say with Greek letters, alpha-beta-gamma. The priest who performed the scooping did not enter with a hemmed garment, a shoe, a sandal, or any other box - to avoid the situation that if he would later become poor, people would say, "This happened to him because he stole!" and if he would become rich, they would say, "He became rich from the proceeds of his stealing!" This illustrates that one must strive to be clear of all suspicions, and even if he is clear in the eyes of God, he must still strive to avoid suspicions in the eyes of men.
Art: The Parable Of The Rich And Poor Man by (after) Frans II Francken