Leviticus 14:4-6

4the priest shall order that two live clean birds, cedar wood, scarlet yarn, and hyssop be brought for the one to be cleansed.

5Then the priest shall command that one of the birds be slaughtered over fresh water1 in a clay pot. 6And he is to take the live bird together with the cedar wood, scarlet yarn, and hyssop, and dip them into the blood of the bird that was slaughtered over the fresh water.