Numbers 19:6
And the priest shall take cedar wood, and hyssop, and scarlet, and cast it into the midst of the burning of the heifer. And the priest shall take cedar wood, and hyssop, and scarlet, and cast it into the midst of the burning of the heifer.
The cedar wood, hyssop, and scarlet belong to the appointed rite for purifying Israel from the ceremonial defilement contracted by contact with death, and that contact with death represented sin. In that rite the cedar, hyssop, and scarlet were used with the cleansing water that was sprinkled upon the people and upon the tent. The red heifer, together with the other offerings that were offered singly, pointed to Christ as the one great offering who voluntarily gave Himself to redeem the sinful world and to purify it through His suffering and His blood. The purification signified by the ceremony is accomplished through Christ's blood and spotless righteousness, by which people are cleansed from sin.