Niddah 48 - A Minor That Never Grows Up
In some rare cases a male or a female never completely matures. This changes some marital laws for them, thus, if a female is twenty but has not sprouted two pubic hairs, she must bring a proof of her age, and will then be considered as forever immature ("aylonit"): yibum (levirate marriage) cannot be done to her, and she does not require halitzah and can marry anyone if her husband dies. Similarly, a man who is twenty but has not sprouted two pubic hairs, must bring a proof of his age, and he then need not perform yibum or be the subject of halitzah .
The lower sign (two pubic hairs) always comes before the upper sign (breast development). When the lower sign is present, the girl can do either halitzah or yibum, and when the upper sign ( small fig stage of development ) is present, we can presume the same - these are the words of the Sages. However, Rabbi Meir disagrees on two counts. If the upper sign is present, according to Rabbi Meir it means nothing, so she cannot halitzah, which only adults can do. And although minor can do yibum, Rabbi Meir does not allow it for a different reason: a minority of people never mature, and Rabbi Meir, who always takes a statistical minority into account, is apprehensive that the girl or a boy will never mature, and their yibum would retroactively violate a serious prohibition, so according to Rabbi Meir they must wait till they fully mature.
When an examination of a girl was required, it was done by a woman.
Art: Rembrandt Van Rijn - A youth in a cap and gorget