Numbers 8:21

Numbers 8 describes the lighting of the seven lamps on the golden candlestick, which Aaron arranged to give light over against it just as the Lord commanded. It then records the cleansing and consecration of the Levites - sprinkling them with water of purifying, shaving them, washing their clothes, and presenting them as a wave offering, with the Israelites laying hands on them as a substitute for the firstborn. The chapter sets the age of Levitical service from twenty-five to fifty, after which they would assist their brethren but no longer do the labor of the service.