03 Ketubot 1/8-10

(8) [In a case where people] saw her conversing [intimately] with a man in the market, [and] they said to her, "What is the nature [i.e., the lineage] of that man?" She says, "He is so and so, and he is a kohen [or of other legitimate descent]." Rabban Gamliel and Rabbi Eliezer say, "She is believed." Rabbi Yehoshua says, "We do not live by [the words of] her mouth. Rather, she is presumed to have been penetrated by a netin [Gibeonites] or a mamzer [the offspring of certain prohibited relationships who may not marry into the general Jewish population], until she brings proof for her words."

(9) [In a case where] she was pregnant, and they said to her, "What is the nature of this fetus [i.e., what is the lineage of the father]?" She replies, "By so and so, and he is a priest." Rabban Gamliel and Rabbi Eliezer say, "She is believed." Rabbi Yehoshua says, "We do not live by [the words of] her mouth. Rather, she is presumed to have had sexual relations with a netin or a mamzer until she brings proof for her words."

(10) Rabbi Yossi said, "It [once] happened that a girl went down to draw water from the spring, and she was raped. Rabbi Yochanan ben Nuri ruled, 'If the majority of the townsmen [were of pure descent and qualified to] marry [into families of the] priesthood, this [girl] may marry into the priesthood.'