Numbers 5:18-20

18and the priest shall set the woman before the LORD, and let the hair of the woman’s head go loose, and put the meal offering of memorial in her hands, which is the meal offering of jealousy: and the priest shall have in his hand the water of bitterness that causeth the curse:

19and the priest shall cause her to swear, and shall say unto the woman, If no man have lain with thee, and if thou hast not gone aside to uncleanness, being under thy husband, be thou free from this water of bitterness that causeth the curse:

20but if thou hast gone aside, being under thy husband, and if thou be defiled, and some man have lain with thee besides thine husband: