Sotah 16A

שילה נוב וגבעון ובית עולמים.

Shiloh, Nob, and Gibeon, and also God House, i.e., the Temple in Jerusalem. The dust for the sota is still brought from the ground of the Sanctuary wherever it is located, even after the Jewish people are no longer in the wilderness.

איסי בן מנחם אומר, אינו צריך: ומה בטומאה קלה לא חלק הכתוב ⁠— בטומאת אשת איש חמורה, לא כל שכן? אם כן מה תלמוד לומר ״בקרקע המשכן״⁠ — שלא יביא מתוך קופתו.

Isi ben Menaḥem says: There is no need to derive this halakha from the verse. It may be learned by an a fortiori inference: With regard to the prohibition against entering the Sanctuary in a state of impurity, a lenient matter for which there is no court-imposed capital punishment, the Torah does not differentiate. It is prohibited for an impure person to enter the Tabernacle no matter where it stands. Therefore, with regard to the impurity of a married woman, which is stringent and carries the penalty of strangulation, all the more so is it not clear that the Torah does not differentiate? The dust must be brought from the Sanctuary no matter where it stands. If so, what is the meaning when the verse states: “And of the dust that is on the floor of the Tabernacle”? It teaches that one should not bring dust from his own basket and place it directly into the water; he must first place it on the floor.

איבעיא להו: אין שם עפר, מהו שיתן אפר? אליבא דבית שמאי לא תיבעי לך, דאמרי: לא מצינו אפר שקרוי ״עפר״.

A dilemma was raised before the rabbis: If there is no dust there, what is the halakha? May one place ashes in the vessel instead? The Talmud responds: There is no need to raise the dilemma if one holds in accordance with the opinion of Beit Shammai, as they say: We never find ashes referred to as dust in the Torah.