Leviticus 14:4-6

then the priest shall command to take for him who is to be cleansed two living and clean birds, cedar wood, scarlet, and hyssop. And the priest shall command that one of the birds be killed in an earthen vessel over running water. As for the living bird, he shall take it, the cedar wood and the scarlet and the hyssop, and dip them and the living bird in the blood of the bird that was killed over the running water.