The water of cleansing

Numbers 19:1-22
The water of cleansing.
A read heifer without defect or blemish and that has never been under a yoke. Then Eleazar the priest is to take some of its blood on his finger and sprinkle it seven time toward the front of the tent of meeting. While he watches, the heifer is to be burned - its hide, flesh, blood and intestines. The priest is to take some cedar wood, hyssop and scarlet wool and throw them onto the burning heifer. After that the priest and the man who burns it must wash his clothes and bathe himself with water, come into the camp, but he will be unclean till evening.
Whoever touches a human corpse will be unclean for seven days. They must purify themselves with the water on the third day and on the seventh day; then they will be clean.
For the unclean person, put some ashes from the burned purification offering into a jar and pour fresh water over them. Then a man who is ceremonially clean is to take some hyssop, dip it in the water and sprinkle the tent and all the furnishings and the people who were there.He must also sprinkle anyone who has touched a human bone or a grave or anyone who has been killed or anyone who has died a natural death.
The ritual with the read heifer is the remedy for defilement by contact with a dead body, described in verses 11-22. To minimize the risk of accidental defilement, tombs were later painted white.
Why?
Touched dead body means unclean and it may bring some disease or ceremony unclean so the Lord asked them to purify themselves through priest.
The heifer mean remedy for defilement. For sins need remedy to erase.
How?
Keep ourselves from sins and confess our sins before the Jesus Christ is the way to purify ourselves.