And the priest shall take holy water
Out of the laver, as the Targums of Onkelos and Jonathan, and so Jarchi and Aben Ezra:
in an earthen vessel;
which held half a log, and that was but a quarter of a pint, or three egg shells; for no more was assigned, to a suspected woman, according to the Misnah F18. Some say only a fourth part: an earthen vessel was made use of, as everything vile and mean was in this affair:
and of the dust that is in the floor of the tabernacle the priest
shall take, and put [it] into the water;
first the water was put in, and then the dust, as Ben Gersom observes: there was a place a cubit square, where was a marble table, and a ring fixed in it, and when he lifted it up he took dust from under it, and put it so as it might be upon the top of the water F19; which was used, either, as the Targum of Jonathan suggests, because the end of all flesh is to come to dust, and so to put her in mind of her original and her end; and in like manner the earthen vessel might signify, that she would be broke to pieces as that vessel; as also it might direct her thoughts to the tempter, by the influence of whose temptation she had been drawn into this sin, dust being the serpent's food; and this being taken off the floor of the tabernacle, might add to the veneration of it, and make it more solemn and awful to drink of it.
The Brenton translation of the Septuagint is in the public domain.