Numbers 3:10, 38

Appoint Aaron and his sons to carry out the duties of the priesthood. But any unauthorized person who goes too near the sanctuary must be put to death.”

The area in front of the Tabernacle, in the east toward the sunrise, was reserved for the tents of Moses and of Aaron and his sons, who had the final responsibility for the sanctuary on behalf of the people of Israel. Anyone other than a priest or Levite who went too near the sanctuary was to be put to death.