Bamidbar - R'vi'i

The Torah tells us that Aharon had four sons but two of them, Nadav and Avihu, died childless. This left only Elazar and Itamar to serve as kohanim alongside their father. G-d told Moshe that the Levites would assist with matters pertaining to the Tabernacle. They would be responsible for all utensils of the Mishkan, but only the kohanim could perform the actual service.

The Levites were replacing the first-born sons, who were originally supposed to fill this role. All first-borns are sanctified to G-d because He spared them during the final plague in Egypt. (See parshas Bo, Exodus chapter 13, for the mitzvah of pidyon haben.)

Author: Rabbi Jack Abramowitz