Rashi on Deuteronomy 22:17/רש"י על דברים כ״ב:י״ז

1ופרשו השמלה AND THEY SHALL SPREAD THE CLOTH [BEFORE THE ELDERS OF THE CITY] — This is a figurative expression: they must make the matter as white (as clear) as a sheet (Sifrei Devarim 237:1; Ketubot 46a).