Rabbi Aba asks Rabbi Shimon why the 'red heifer' in "a red heifer, faultless without blemish" is compared to the calf and the lamb and why it should be cleansed just through roasting it. Rabbi Shimon says the essence of the message is that a clean thing can be brought out of an unclean thing. The heifer was unclean, but by burning her to ashes she became clean. She had to be burned to ashes because it is like the verse: "and you shall tread down the wicked, for they shall be ashes under the soles of your feet." When water was sprinkled on the ashes they became clean. The secret of the clean water is the verse: "water of purifying (sin)." After judgment was executed on the heifer she became clean and the Holy Spirit had dominion. The spirit of defilement was no longer found in the camp.