"This is the law that applies when a person dies in a tent." (Numbers 19:14)
God gives the ordinance of the red heifer, one of the most enigmatic rites in the Torah. A red heifer without defect or blemish and that has never been under a yoke is to be slaughtered outside the camp, burned to ashes with cedar wood, hyssop, and scarlet wool. The ashes are stored for use in the water of purification: anyone who becomes ceremonially unclean through contact with a dead body is to be sprinkled with this water on the third and seventh days and will then be clean. Without this purification the defiled person cannot enter the camp of the LORD's presence.
The paradox of the red heifer rite is noted by the rabbis and by the Church Fathers: the ashes that purify the unclean make the one who prepares them unclean. This paradox points forward to the Cross: the Letter to the Hebrews explicitly invokes the red heifer as the type of Christ's sacrifice, whose blood cleanses the conscience from dead works more effectively than the ashes of an animal (Hebrews 9:13-14). The one who bears the uncleanness of others in order to purify them is the pattern of the Lamb of God who takes away the sin of the world. The Catechism identifies this as one of the richest sacrificial types in the Old Testament (CCC 613). This is the law that applies when a person dies in a tent. The pollution of death requires the purification of sacrifice.
Brothers and sisters, the ashes that purify the unclean make the one who prepares them unclean. The one who bore our impurity to cleanse us was Christ, who became sin for us so that we might become the righteousness of God. You are clean. You have been sprinkled on the third day and the seventh. Receive that cleansing and live from it.
Lord Jesus, you became the red heifer, bearing our uncleanness to purify us from every contact with death. Sprinkle us with the water of your sacrifice. Cleanse our consciences from dead works to serve the living God. Through Christ our Lord. Amen.