Numbers 5:17
And the priest shall take holy water in an earthen vessel; and of the dust that is in the floor of the tabernacle the priest shall take, and put it into the water: And the priest shall take holy water in an earthen vessel; and of the dust that is in the floor of the tabernacle the priest shall take, and put it into the water:
The bitter water used in the offering of jealousy was made by taking holy water in an earthen vessel and having the priest put into it dust taken from the floor of the tabernacle. It was given by the priest to a wife suspected of unfaithfulness when there were no witnesses to prove the matter. With the water was presented an offering of a tenth of an ephah of barley meal with no oil and no frankincense, an offering of memorial bringing iniquity to remembrance.
The rite was not appointed to make atonement for sin but to discover sin and to prove innocence or guilt. If the woman was innocent the drink did her no harm, but if she was guilty it brought upon her a condition leading to speedy and dreadful death, and by this means God rid Israel of even the suspicion of impurity. As a type, the rite shows that sin is not only the open act but the inward condition of heart and character that bears fruit in open transgression.