How Does Moses End Their Preparation Season With Numbers Chapter Eight?

Moses' preparation for the nation of Israel before they are entering the tabernacle. The Levites aren't anointed with oil, which is taken with the priests to prepare them to minister inside theTabernacle. So it's like you could say the Levites are living sacrifices in the way that they're serving the Lord. They got a retire for retirement age, which I think points to the fact that this will continue on generations after generations after generations.