This is a permanent rule for everyone. The man who sprinkles the water of purification must wash his clothes, and anyone who touches the water of purification will be unclean until the evening.
In the Tent of Meeting, outside the veil in front of the Testimony, Aaron and his sons are to keep the lamps burning in the Lord's presence from evening until morning. This requirement is to be observed by the Israelites for all generations.
If you eat anything from the dead body you must wash your clothes and you will be unclean until the evening. If you pick up the dead body you must wash your clothes and you will be unclean until the evening.
The Levites are to carry out the work in the Tent of Meeting, and they must take responsibility for any sins involved. This is a permanent rule for all future generations. The Levites won't receive a share of land among the Israelites.
The man who collected the ashes of the cow shall also wash his clothes, and he will remain unclean until the evening. This is a permanent rule for the Israelites and for the foreigner that lives with them.
They're just religious regulations—about food and drink, and various ceremonies involving washing—which were put in place until the time of God's new way of relating to him.