The Torah in Parashat Bamidbar (4:19) commands that the Leviyim should be assigned “Ish Ish Al Masa’o” – each person to a particular job. Later in the Book of Bamidbar (18:3), the Torah forbids the Leviyim from approaching the altar and other areas of the Mikdash to serve, a role assigned exclusively to the Kohanim (“Ach El Keleh Ha’kodesh Ve’el Ha’mizbe’ah Lo Yikrabu”). The Sages understood these verses as establishing a prohibition for a Kohen or a Levi to perform a task assigned to a different Kohen or Levi. The Gemara (Arachin 11b) tells the story of Rabbi Yehoshua Bar Hananya, a Levi, who volunteered to help his fellow Levi, Rabbi Yohanan Ben Gudgoda, with his job locking the gates of the Bet Ha’mikdash. Rabbi Yohanan admonished him to step back, as he would otherwise be liable to capital punishment for violating this Biblical command. This story demonstrates that it is forbidden not only for a Levi to perform a Kohen’s role, but also for a Levi to perform a fellow Levi’s role. The Sefer Ha’hinuch explains that the Torah introduced this prohibition because very often, when a job is assigned to two people, it ends up not getting done, as each assumes that the other will tend to it. Indeed, the Gemara (Baba Batra 24b) states, “A pot belonging to partners is neither hot nor cold” – meaning, if a pot of raw food is given to two chefs to cook, it remains uncooked. Therefore, in order to ensure that none of the duties in the Mikdash are neglected, the Torah commanded each Kohen and each Levi to tend to his assigned role, and not perform anybody else’s job. This way, each Kohen and Levi knows that he and only he is responsible for completing his assigned task. In all, fifteen areas of responsibility were assigned to the Kohanim and Leviyim: 1) An official was assigned to keep track of the time, and make sure that everything was done at its proper time. 2) An official was assigned to supervise the opening and locking of the gates. 3) An official oversaw the watchmen who were stationed at various posts inside and outside the Bet Ha’mikdash. 4) An official was in charge of the Meshorerim – the Leviyim who would sing and play music during the offering of sacrifices. 5) An official was assigned over the lottery which was held to determine which Kohen would perform the various rituals in the Bet Ha’mikdash that day. 6-7) A cashier was appointed to receive money from people who needed to purchase wine for the libations accompanying the sacrifices, and would give them a certificate with which to obtain wine. This certificate was then given to another official, who was in charge of giving wine to the customers. 8-9) Similarly, two officials were assigned to sell birds to those who needed to offer bird sacrifices, such as women after childbirth. One official would receive the money, and another would give the birds to the customers. 10) A physician was on call to care for Kohanim who fell ill. 11) Well-diggers were appointed to prepare wells and ensure a sufficient supply of fresh water for pilgrims coming to Jerusalem. 12) There was a family in charge of baking the Lehem Ha’panim, the special bread placed on the Shulhan (table) inside the Bet Ha’mikdash. 13) Another family was in charge of preparing the Ketoret, the incense offered on the altar inside the Bet Ha’mikdash. 14) There was also a family in charge of weaving the Parochet, the cloth partition that divided between the two areas inside the Bet Ha’mikdash. 15) Yet another family was in charge of preparing the special garments worn by the Kohanim. Once somebody was assigned to one of these jobs, he was not permitted to do a different job. This prohibition applies only in the times of the Bet Ha’mikdash, and to the Kohanim and Leviyim. A Levi who does a Kohen’s job, or a job assigned to other Leviyim but not to him, is liable to Mita Bi’ydeh Shamayim (death by G-d’s hand, as opposed to execution by the court). A Kohen who does a job assigned to a Levi has transgressed this Biblical