The red heifer, which was sacrificed on the Mount of Olives, had to be “without spot, wherein is no blemish and upon which never came yoke” (Num. 19. 2). The ashes, mixed with water, were used to sprinkle people who were defiled in order to cleanse them ritually. The officiating priest had to catch the blood of the heifer and sprinkle it seven times towards the Holy of Holies (or the Tabernacle in pre-Temple times). This drawing shows the line of vision from the top of the Mount of Olives to the door of the Temple.
The ashes of a heifer that were sprinkled on unclean persons, are mentioned in Hebrews 9.13,14, indicating, however, the superiority of the cleansing powers of the blood of Christ.