2,015. Acquiring the Dust

Hilchos Sotah 4:12

If the water for a suspected woman is left overnight, it is rendered invalid. If the dust was put in the vessel before the water, it is invalid. If there’s no dust in the Heichal (the Sanctuary of the Temple), dust is brought from outside the Heichal and left in the Heichal. Some of it is then taken and placed on the water. One may not use ash but one may use rotten wood, which is considered the functional equivalent of dust.

Hilchos Sotah 4:13

One may not dig with an axe in the Heichal in order to acquire dust. Numbers 5:17 specifies “dust that is on the ground of the Tabernacle.” If one did dig to acquire dust, it is valid.