At Marah
And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah. (Exodus 15:23)
A ceremonial water used by the priest
And the priest shall set the woman before the Lord, and uncover the woman's head, and put the offering of memorial in her hands, which is the jealousy offering: and the priest shall have in his hand the bitter water that causeth the curse: And the priest shall charge her by an oath, and say unto the woman, If no man have lain with thee, and if thou hast not gone aside to uncleanness with another instead of thy husband, be thou free from this bitter water that causeth the curse: But if thou hast gone aside to another instead of thy husband, and if thou be defiled, and some man have lain with thee beside thine husband: Then the priest shall charge the woman with an oath of cursing, and the priest shall say unto the woman, The Lord make thee a curse and an oath among thy people, when the Lord doth make thy thigh to rot, and thy belly to swell; And this water that causeth the curse shall go into thy bowels, to make thy belly to swell, and thy thigh to rot: And the woman shall say, Amen, amen. And the priest shall write these curses in a book, and he shall blot them out with the bitter water: And he shall cause the woman to drink the bitter water that causeth the curse: and the water that causeth the curse shall enter into her, and become bitter. Then the priest shall take the jealousy offering out of the woman's hand, and shall wave the offering before the Lord, and offer it upon the altar: And the priest shall take an handful of the offering, even the memorial thereof, and burn it upon the altar, and afterward shall cause the woman to drink the water. And when he hath made her to drink the water, then it shall come to pass, that, if she be defiled, and have done trespass against her husband, that the water that causeth the curse shall enter into her, and become bitter, and her belly shall swell, and her thigh shall rot: and the woman shall be a curse among her people. (Numbers 5:18-27)