The Need For Cleansing

What do the ashes signify as far as salvation is concerned? Why does the Holy Spirit do a work in a sinner and what is the effect? Why was the red heifer offered only one time according to Scripture? Why would someone not want to purify themselves? What were the two conditions found that required this cleansing? What is the number 7 the symbol of in Scripture? What was the source of the water of separation? How do we touch death every day?