Numbers 18:22-23

“From now on, no Israelites except priests or Levites may approach the Tabernacle. If they come too near, they will be judged guilty and will die. Only the Levites may serve at the Tabernacle, and they will be held responsible for any offenses against it. This is a permanent law for you, to be observed from generation to generation. The Levites will receive no allotment of land among the Israelites