John Wesley on Numbers 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.