Aaron is commanded to raise light in the lamps of the menorah, and the tribe of Levi is initiated into the service in the Sanctuary.

A “Second Passover” is instituted in response to the petition “Why should we be deprived?” by a group of Jews who were unable to bring the Passover offering in its appointed time because they were ritually impure. G‑d instructs Moshe on the procedures for Israel’s journeys and encampments in the desert, and the people journey in formation from Mount Sinai, where they had been camped for nearly a year.

The people are dissatisfied with their “bread from heaven” (the manna), and demand that Moshe supply them with meat. Moshe appoints 70 elders, to whom he imparts of his spirit, to assist him in the burden of governing the people. Miriam speaks negatively of Moshe and is punished with leprosy; Moshe prays for her healing, and the entire community waits seven days for her recovery.

Source: chabad.org