So we begin, or maybe continue to see, these laws of purification that can be confusing and as you read the Bible from the eyes of a 21st century Christian, bewildering. The laws are simple. Every year the people of Israel are to sacrifice a red cow, one that has never worked the field, as a purification offering. Whoever is involved in this offering will be unclean until the evening.
Then there is a transition to what do we do when we come into contact with the dead. We see a whole list of commandments that are meant to be kept and are not to be overlooked. If you do not follow what is written then it means that the person "shall be cut off from Israel." So, not really something to mess around with. Anyone who interacts with a dead person or with death is unclean for a week. But they can come back into good graces by purifying after 3 days and then again after 7 days. All you have to do is follow the rules and everything will work out fine.
I don't think we have a life lesson from that last sentence, but some do. Our Christian life is not built around a set of rules. Our Christian life is built around a relationship with Jesus Christ which is not founded on rules but rather on the love that he has for us which was seen when he died for us.