From Chabad.org: In this week’s Torah reading, Beha’alotecha, G‑d instructs Aaron concerning the Tabernacle Menorah lighting. The Levites are initiated into the Tabernacle service. The “Second Passover” is instituted. At G‑d’s behest, Moses makes two trumpets, and is instructed how and when to use them. The Israelites leave Mount Sinai, and proceed towards the Land of Canaan. The people unreasonably complain about their “frugal” manna diet and receive a meat supplement, albeit with tragic results. Moses appoints seventy elders to assist him in bearing the burden of the people. Miriam speaks negatively about Moses and is punished with tzara’at (a skin disease).
In the first Aliya G‑d commands Aaron to light the golden Tabernacle Menorah on a daily basis. Moses is then commanded to initiate the Levites into Tabernacle service. This inauguration procedure included shaving their bodies, immersion in a mikvah, and the offering of certain sacrifices.