Leviticus 14:4-7

the priest shall command them to take for him who is to be cleansed two live clean birds and cedarwood and scarlet yarn and hyssop. And the priest shall command them to kill one of the birds in an earthenware vessel over fresh water. He shall take the live bird with the cedarwood and the scarlet yarn and the hyssop, and dip them and the live bird in the blood of the bird that was killed over the fresh water. And he shall sprinkle it seven times on him who is to be cleansed of the leprous disease. Then he shall pronounce him clean and shall let the living bird go into the open field.