Sanhedrin 69B

אמאי? אימא: איילונית היא, ואדעתא דהכי לא קדיש! אלא, לאו דאמרינן: זיל בתר רובא, ורוב נשים לאו איילונית נינהו.

R' Yirmeya of Difti explains how this Mishnah demonstrates that one follows the majority even in cases of capital law: Why is a man who had sex with a 3-year-old girl who was married to another man liable to receive the death penalty? Say that perhaps it will turn out that she is a sexually underdeveloped woman [ailonit] who is incapable of bearing children, and her husband did not betroth her with this understanding; and consequently the marriage is null, as it was entered into in error. Therefore, a man who had sex with her should not be liable to receive the death penalty for adultery. Rather, is it not that we say that one follows the majority, and the majority of women are not sexually underdeveloped women, and therefore the assumption is that the betrothal was valid? This is proof that even in cases of capital law one follows the majority.

לא, מאי ״חייב עליה״ דקתני? קרבן.

The Talmud refutes this claim: No; rather, what is the meaning of that which is taught in the Mishnah: And if she is married, a man other than her husband is liable for having sex with her due to violation of the prohibition against sex with a married woman? This means that if a man unwittingly had sex with a 3-year-old girl who was married to another man, he is liable to bring a sin-offering, but there is no liability to receive the death penalty based on a majority.

והא ״מומתין על ידה״ קתני? בבא עליה אביה.

The Talmud asks: But wasn’t it taught in the Mishnah: And if one of any of those with whom sex are forbidden, which are enumerated in the Torah, had sex with her, the man is executed by the court for having sex with her? The Talmud answers: This is referring to a case where her father or some other close relative had sex with her, so that the prohibition is incest, rather than adultery.