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."
Cross References (ranked by relevance)
Then shall the priest command to take for him that is to be cleansed two birds alive and clean, and cedar wood, and scarlet, and hyssop:
Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow.
And he shall take to cleanse the house two birds, and cedar wood, and scarlet, and hyssop:
As for the living bird, he shall take it, and the cedar wood, and the scarlet, and the hyssop, and shall dip them and the living bird in the blood of the bird that was killed over the running water:
Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.