Numbers 5:17-18

17Then the priest will take holy water in a piece of pottery and put some dust from the floor of the tent into the water.

18The priest will bring the woman into the Lord’s presence and loosen her hair. In her hands he will put the offering used for a confession (that is, the grain offering brought because of the husband’s jealousy). The priest will hold in his hands the bitter water that can bring a curse.