"We have seen that these natural descents are aspects of ascent. Why, however, must this process be accompanied by immersion in a mikvah, and what has water to do with changing one’s status from tamei, 'impure,' to tahor, 'pure'?" (source)

"One who is tahor can enter the sanctuary, the dwelling-place of God’s presence and the heart of Israelite ritual. One who is tamei cannot." (source)

"Any keilim, utensils or appliances, that now become tamei will require immersion in a mikveh or spring, and will become tahor again at the subsequent nightfall." (source)