Sin cannot be tolerated by God. Someone will be held accountable for it. Under the Law of Moses, the priests bore the weight of the sins of the people once the proper sacrifices had been presented. The priests and ultimately, the high priest then made the necessary offerings for the people. Christ is our High Priest today. He sacrificed Himself once for all, to bear the sins of all who accept Him.
God required the first and best offerings from the Israelites. The priests and other Levites were to perform the rituals associated with those offerings and to care for the tabernacle. As compensation for not having a portion of the Promised Land, the Levites were permitted to eat of those sacrifices and receive the tithes of the people. They served their duties and received the best of the produce of the land. The Levites then were required to offer tithes of the best from those gifts.
Uncleanness also was not allowed in the camp. Arrangements were made to provide cleansing for anyone who became unclean. A red heifer without blemish and that had never been yoked was to be ceremonially slaughtered and burnt. Its ashes were to be stored in a clean place outside the camp. Some of the ashes of that heifer were to be mixed with running water and sprinkled upon the unclean person or thing for purification on the third day. On the seventh day, that person must wash his clothes and bathe himself in water. He would be clean at evening.
A person who did not submit for cleansing would be cut off from the assembly. Today, a person who does not submit to the cleansing waters of baptism will remain outside the assembly/church.