Ketubot 23 - Captured woman
Once some women were captured by idolaters and brought to Nahardea to be ransomed. The father Shmuel placed guards over them, so that they would not be violated by their captors. Shmuel said to his father, "And until now who guarded them?" This was logical but not according to human dignity, so the father of Shmuel remarked, "And if these were your daughters, would you treat them as lightly?"
Occasional remark by a righteous may take effect, and later the daughters of Shmuel were indeed captured. The captors brought them to Israel for ransom. The knowledgeable women left their captors outside and entered the court of Rav Chanina. Each one of them declared, "I was captured but I am pure." According to the previously stated rule that "the mouth that forbids is the mouth that permit," they were believed. When their captors entered afterwards, it made no difference.
Rav Chanina said, "These are children of a legal master," and indeed it was found out that they were the daughters of Shmuel.
If two women were captured by idolaters, but in this case there were witnesses to their capture, and each of them says, "I was captured but I am pure" - she is not believed, because we know about her capture independently, and not only from her words. However, if each testifies about the other that she is pure, then they are believed.
Art: The Capture by Franz Roubaud