Numbers 19:7, commentary and pictures

The priest who carried out the red-heifer purification had to wash his clothes and bathe his flesh in water, and afterward he could come into the camp, yet he remained ceremonially unclean until evening. No impurity of person or of clothing was allowed, so anyone with personal uncleanness was shut out of the camp until evening and had to cleanse himself and his clothing before entering. The rite belonged to an offering made for the congregation's purification from defilement contracted through contact with death, and that defilement represented sin.

The heifer's sacrifice pointed to Christ's offering to redeem from the pollution of sin and to cleanse from sin. Its death and the priest's sprinkling of its blood carry that meaning of Christ's sacrifice and cleansing, while the particular washing and the priest's uncleanness until evening are not given that explanation. No impurities were to be left on the premises for a great distance around the encampment, lest He pass by and see uncleanness.

The cleanliness required of ancient Israel is required no less of His people now. Neglect of cleanliness brings disease, with stubborn fevers and violent disease, with sickness and premature death, having their cause in uncleanness.