[In the case of a] 20-year-old [female] who has not brought two [pubic] hairs —- she shall bring proof that she is 20 years old, and she [must also exhibit the signs of] an aylonis, [and then,] she neither performs chalitzah nor is taken as a yibum wife.  [In the case of a] 20-year-old [male] who has not produced two [pubic] hairs —- he shall bring proof that he is 20 years old, and he [must also exhibit the signs of] a saris, [and then,] he neither performs chalitzah nor takes [his brother’s widow as] a yibum-wife; these are the words of Beis Hillel.  Beis Shammai say: [The aforementioned rulings apply to] this [female] and that [male when they are] 18 years old.  R’ Eliezer says: [The law of] the male accords with the opinion of Beis Hillel, and [the law of] the female accords with the opinion of Beis Shammai, for the woman hastens to come [to physical maturity] before the man.

[When] the lower sign comes before the upper [sign] comes, [a girl] performs either chalitzah or yibum. [When] the upper [sign] comes before the lower [sign] comes —- even though this is not possible —- R’ Meir says: She performs neither chalitzah nor yibum. But the Sages say: She performs either chalitzah or yibum, because they have said: It is possible for the lower [sign] to come before the upper [sign] has come, but it is not possible for the upper [sign] to come before the lower [sign] has come.

Similar to this, every earthenware vessel that lets in [liquid], lets out [liquid], but there can be [an earthenware vessel] that lets out [liquid] but does not let in [liquid].  Every limb that has a fingernail has a bone, but there can be [a limb] that has a bone but does not have a fingernail.

Every [object] that contracts “treading” tumah contracts corpse tumah, but there can be [an object] that contracts corpse tumah but does not contract “treading” tumah.

Everyone who is eligible to judge capital cases is eligible to judge monetary cases, but there can be [someone] who is eligible to judge monetary cases but is not eligible to judge capital cases.  Everyone who is fit to judge is fit to testify, but there can be [someone] who is fit to testify but is not fit to judge.

Every [food] that is subject to tithes contracts food tumah, but there can be [a food] that contracts food tumah but is not subject to tithes.

Every [growth] that is subject to pe’ah is subject to tithes, but there can be [a growth] that is subject to tithes but is not subject to pe’ah.

Every [animal] that is subject to reishis hageiz is subject to the [Priestly] gifts, but there can be [an animal] that is subject to the [Priestly] gifts but is not subject to reishis hageiz.

Every [growth] that is subject to biur is subject to sheviis, but there can be [a growth] that is subject to sheviis but is not subject to biur.

Every [fish] that has scales has fins, but there can be [a fish] that has fins but does not have scales.  Every [animal] that has horns has split hooves, but there can be [an animal] that has split hooves but does not have horns.

Everything that requires a blessing after it requires a blessing before it, but there can be [something] that requires a blessing before it but does not require a blessing after it.

A girl who produced two hairs can perform either chalitzah or yibum, and she is obligated in all of the commandments stated in the Torah.  Similarly, a boy who produced two hairs is obligated in all of the commandments stated in the Torah. He is eligible to be a ben sorer umoreh from the time he produces two hairs until the beard grows around, [which refers to] the lower beard, not the upper one, for the Sages spoke euphemistically.  A girl who produced two hairs cannot perform mi’un. R’ Yehudah says: Until the black appears abundant.

The two hairs that are stated regarding the [red] cow, regarding [tzaraas] afflictions, and those stated elsewhere, [must be long] enough to bend their top to their root; these are the words of R’ Yishmael. R’ Elazar says: [Long] enough to be caught by a fingernail. R’ Akiva says: [Long] enough to be removed with scissors.

[A woman] who finds a stain is impaired, and she must be concerned for zivah; these are the words of R’ Meir. The Sages say: Stains are not subject to [concern for] zivah.

[A woman] who experiences [a discharge] during bein hashemashos on the eleventh day [of her zivah period, either at] the beginning of the niddah [period] or the end of the niddah [period], [or at] the beginning of the zivah [period] or the end of the zivah [period], [or on] the fortieth day for a male, or [on] the eightieth day for a female, [and] all these [discharges] occurred during bein hashemashos, these [women] are confused.  R’ Yehoshua said: Before you rectify the foolish ones, rectify the competent ones!

The blood of a niddah and the flesh of a corpse convey tumah [when they are] moist and they convey tumah [when they are] dry. But a zivah emission, the phlegm [of a zav], the saliva [of a zav], a sheretz, an [animal] carcass, and semen convey tu-mah [when they are] moist, but they do not convey tumah [when they are] dry. But if they can be soaked [in water] and re-vert back to the way they were, they convey tumah [when they are] wet and they convey tumah [when they are] dry. And [for] how long [must] they be soaked? In warm water for twenty-four hours. R’ Yose says: [Regarding] dry flesh of a corpse that cannot be soaked and revert back to what it was, [it is] tahor.