Numbers 19:12-13

12They must purify themselves with the water on the third day and on the seventh day; then they will be clean. But if they do not purify themselves on the third and seventh days, they will not be clean. 13If they fail to purify themselves after touching a human corpse, they defile the Lord’s tabernacle. They must be cut off from Israel. Because the water of cleansing has not been sprinkled on them, they are unclean; their uncleanness remains on them.