Numbers 19:9

it shall be kept i.e. the ashes, for which the Heb. word is singular, not plural.

a water of impurity] i.e. a water for the removal of impurity. Cf. -water of sin" (Numbers 8:7). The word niddâh, -impurity," signifies something loathsome or abominable.

it is a sin-offering The cow (not the water) could be called a sin-offeringbecause it was burnt; but, since the ashes are the object of chief importance, the word hattâ"th(-sin-offering") must be understood in the more general sense of -something which removes sin." LXX. ἅγνισμα.