Ketubot 10B

גיהוץ שלנו, ככבוס שלהם. ואי אמרת ניעבד גיהוץ ⁠— מעברא ליה חומרתא.

Our calendering in Babylonia, which includes passing an abrasive stone over the garments to scrape off dirt, is like their laundering in Eretz Israel, and only in that manner do the garments in Babylonia reach that level of cleanliness. And if you say: Let us perform the process of calendering on cloths brought as proof that she was not a virgin, the stone removes any trace of blood. Therefore, the process would be ineffective.

ההוא דאתא לקמיה דרבן גמליאל בר רבי, אמר ליה: רבי, בעלתי ולא מצאתי דם. אמרה ליה: רבי, עדיין בתולה אני. אמר להן: הביאו לי שתי שפחות, אחת בתולה ואחת בעולה. הביאו לו, והושיבן על פי חבית של יין, בעולה ⁠— ריחה נודף, בתולה ⁠— אין ריחה נודף. אף זו הושיבה ולא היה ריחה נודף. אמר לו: לך זכה במקחך.

The Talmud relates: A certain man who came before Rabban Gamliel bar R' Yehuda HaNasi said to him: my teacher! I had sex and did not find blood. The bride said to him: my teacher! I am still a virgin. Rabban Gamliel bar R' Yehuda HaNasi said to them: Bring me two female slaves, one a virgin and one a non-virgin, to conduct a trial. They brought him the two female slaves, and he seated them on the opening of a jug of wine. From the non-virgin, he discovered that the scent of the wine in the jug diffuses from her mouth; from the virgin he discovered that the scent does not diffuse from her mouth. Then, he also seated that bride on the jug, and the scent of the wine did not diffuse from her mouth. Rabban Gamliel bar R' Yehuda HaNasi said to the groom: Go take possession of your acquisition, as she is a virgin.

ונבדוק מעיקרא בגווה? גמרא הוה שמיע ליה, מעשה לא הוה חזי, וסבר דלמא לא קים ליה בגווה דמלתא שפיר, ולאו אורח ארעא לזלזולי בבנות ישראל.

The Talmud asks: Since Rabban Gamliel was familiar with this method of examination, let him use it to examine her initially. Why was the trial with the female slaves necessary? The Talmud answers: He learned that it was effective through tradition; however, he had never seen it in action, and he thought perhaps he was not sufficiently expert in that manner of examination, and it is improper conduct to demean Jewish women by subjecting them to that indignity for naught. Once he established the effectiveness of that method, he proceeded to examine the bride to resolve the matter.