And the priest shall take {h} 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:

(h) Which also is called the water of purification of sprinkling, read Nu 19:9.

Wesley's Notes

5:17 Holy water - Water of purification appointed for such uses. This was used, that if she were guilty, she might be afraid to add profaneness to her other crime. An earthen vessel - Because, after this use, it was to be broken in pieces, that the remembrance of it might be blotted out as far as was possible. Dust - An emblem of vileness and misery. From the floor of the tabernacle - Which made it holy dust, and struck the greater terror into the woman, if she were guilty.

Jamieson-Fausset-Brown Bible Commentary

17, 18. the priest shall take holy water-Water from the laver, which was to be mixed with dust-an emblem of vileness and misery (Ge 3:14; Ps 22:15).

in an earthen vessel-This fragile ware was chosen because, after being used, it was broken in pieces (Le 6:28; 11:33). All the circumstances of this awful ceremony-her being placed with her face toward the ark-her uncovered head, a sign of her being deprived of the protection of her husband (1Co 11:7)-the bitter potion being put into her hands preparatory to an appeal to God-the solemn adjuration of the priest (Nu 5:19-22), all were calculated in no common degree to excite and appall the imagination of a person conscious of guilt.

Matthew Henry's Concise Commentary

5:11-31 This law would make the women of Israel watch against giving cause for suspicion. On the other hand, it would hinder the cruel treatment such suspicions might occasion. It would also hinder the guilty from escaping, and the innocent from coming under just suspicion. When no proof could be brought, the wife was called on to make this solemn appeal to a heart-searching God. No woman, if she were guilty, could say Amen to the adjuration, and drink the water after it, unless she disbelieved the truth of God, or defied his justice. The water is called the bitter water, because it caused the curse. Thus sin is called an evil and a bitter thing. Let all that meddle with forbidden pleasures, know that they will be bitterness in the latter end. From the whole learn, 1. Secret sins are known to God, and sometimes are strangely brought to light in this life; and that there is a day coming when God will, by Christ, judge the secrets of men according to the gospel, Ro 2:16. 2 In particular, Whoremongers and adulterers God will surely judge. Though we have not now the waters of jealousy, yet we have God's word, which ought to be as great a terror. Sensual lusts will end in bitterness. 3. God will manifest the innocency of the innocent. The same providence is for good to some, and for hurt to others. And it will answer the purposes which God intends.