Kiddushin 81A

לאתרויי ביה.

how to warn him not to have sex with her, since that would neutralize the effectiveness of the examination of the waters.

אמר רב יהודה אמר רב: לא שנו אלא בעיר, אבל בדרך ⁠– עד שיהיו שלשה, שמא יצטרך אחד מהם להשתין, ונמצא אחד מתייחד עם הערוה. נימא מסייע ליה: מוסרים לו שני תלמידי חכמים שמא יבא עליה בדרך. תרי ואיהו, הא תלתא! התם כי היכי דניהוו עליה סהדי.

Rav Yehuda says that Rav says: A baraita states that two men may seclude themselves with one woman only in a city, where others are present, but on the road it is not permitted unless there are 3. Why are two men insufficient on the road? Perhaps one of them will need to urinate and will walk away, and it will turn out that one person will be secluded with a woman forbidden to him. The Talmud suggests: should we say the Mishnah quoted above supports him: They provide him with two Torah scholars to accompany them lest he have sex with her along the way? He and two Torah scholars are 3, which indicates that there is a requirement for 3 men when they are traveling. The Talmud answers: That is no proof, as there, in the case of the sota, there is a requirement for an additional two men in order that they should serve as witnesses about him, to testify whether or not he had sex with her along the way.

רב ורב יהודה הוו קאזלי באורחא, הוה קאזלא ההיא אתתא קמייהו. אמר ליה רב לרב יהודה: דל כרעיך מקמי גיהנם. אמר ליה: והא מר הוא דאמר בכשרים שפיר דמי! אמר ליה: מי יימר דבכשרים כגון אנא ואת? אלא כגון מאי? כגון רבי חנינא בר פפי וחביריו.

The Talmud relates: Rav and Rav Yehuda were walking along the way, and a certain woman was walking ahead of them. Rav said to Rav Yehuda: Raise your feet and walk quickly away from Gehenna so that we do not remain secluded with her. Rav Yehuda said to him: But wasn’t it you, Master, who said that it is permitted in the case of men of fit morals? Rav said to him: Who says that I referred to men of fit morals such as you and me? Rav Yehuda responded: Rather, such as whom? Rav answered: Such as R' Ḥanina bar Pappi and his colleagues, who have proven that they can withstand temptation (see 39b). All other people are not trusted in this matter.