Numbers 5:11-15

Then the LORD said to Moses, “Speak to the Israelites and say to them: ‘If a man’s wife goes astray and is unfaithful to him so that another man has sexual relations with her, and this is hidden from her husband and her impurity is undetected (since there is no witness against her and she has not been caught in the act), and if feelings of jealousy come over her husband and he suspects his wife and she is impure—or if he is jealous and suspects her even though she is not impure— then he is to take his wife to the priest. He must also take an offering of a tenth of an ephah of barley flour on her behalf. He must not pour olive oil on it or put incense on it, because it is a grain offering for jealousy, a reminder-offering to draw attention to wrongdoing.