And the LORD said to Moses,
"Say to the people of Israel: 'Suppose a man's wife goes astray and is unfaithful to her husband.
Suppose she sleeps with another man, but there is no witness since she was not caught in the act.
If her husband becomes jealous and suspicious of his wife, even if she has not defiled herself,
the husband must bring his wife to the priest with an offering of two quarts of barley flour to be presented on her behalf. Do not mix it with olive oil or frankincense, for it is a jealousy offering -- an offering of inquiry to find out if she is guilty."
References for Numbers 5:15
"'The priest must then present her before the LORD.
He must take some holy water in a clay jar and mix it with dust from the Tabernacle floor.
When he has presented her before the LORD, he must unbind her hair and place the offering of inquiry -- the jealousy offering -- in her hands to determine whether or not her husband's suspicions are justified. The priest will stand before her, holding the jar of bitter water that brings a curse to those who are guilty."
The priest will put the woman under oath and say to her, "If no other man has slept with you, and you have not defiled yourself by being unfaithful, may you be immune from the effects of this bitter water that causes the curse.
But if you have gone astray while under your husband's authority and defiled yourself by sleeping with another man" --
at this point the priest must put the woman under this oath -- "then may the people see that the LORD's curse is upon you when he makes you infertile.
References for Numbers 5:21