Niddah 6:11-12

Niddah 6:11

A girl who has grown two pubic hairs may perform yibum or chalitzah and she is obligated in all mitzvos in the Torah. Similarly, a boy who has grown two pubic hairs is obligated in all mitzvos in the Torah. He is fit to be a “stubborn and rebellious son” (ben soreir u’moreh) from the time he grows two pubic hairs until he grows a full beard; this euphemistically refers to public hair rather than facial hair. A girl who has grown two pubic hairs may no longer unilaterally refuse an existing marriage (mi’un); Rabbi Yehuda says she may do so until black (i.e., hair) covers the greater part of her genital region.

Niddah 6:12

Rabbi Yishmael says that the two hairs mentioned vis-à-vis the red heifer, tzaraas (“leprosy”) and elsewhere means hairs that can be bent so that their tips touch their roots. Rabbi Elazar says it means hairs that can be cut with one’s nails. Rabbi Akiva says it means hairs that can be removed using scissors.