Mikvaos 9:3 - 9:4

ובית הסתרים באיש – for a man is not stringent [concerning this part of his body]. And even a woman is not stringent unless she is married as we have explained (see Mishnah 2 above).

ושאינו מקפיד עליו אינו חוצץ – and for him as long as it isn’t on the majority of his body. And the legal decision regarding interposition – the majority of the body and he is stringent about it, it interposes according to the words of the Torah. A minority thereof, that is to say, if the thing that interposes is in the minority of the body even though he is stringent/he is mindful of it , it does not interpose according to the words of the Torah. But the Sages decreed that on the majority [of the body] and he is not mindful about it because of the majority that he is mindful about, and on the minority that he is mindful about also because of the majority that he is mindful about. But they did not make a decree regarding the minority that he is not mindful about because of the minority that he is mindful of, for this is the body of the decree and we hold that we make a decree on a preventive measure in order to prevent the violation of another preventive measure.

לפלוף שבעין – with that which is moist that dos not interpose, [but] with dry, it interposes, for outside of the eye that is above (see Mishnah 2), whether dealing with something moist or dry, it interposes. And the reason for this is that outside of the eye, a person is mindful about it whether it is moist or whether it is dry, [whereas] within the eye, a person is mindful of something dry, but something moist, he is not mindful of it.

כשות של קטן (downy hair growth of a youth before puberty) – a kind of hair that originates within the flesh of young boys , similar to the hair that originates on cucumbers that we call FAKORS in Arabic. And this hair is called the tuft/fine hairs of cucumbers in the language of the Mishnah (i.e., cucumbers or melons in an early stage when they are pubescent), such is the hair of young boys that is similar to it which is called the down hair growth of a youth before puberty, but the women call it the hair of an imbecile.

לא טמא – if ritual impurity did come in contact with that hair, the young child is not defiled.

ולא מטמא – if the young boy was ritually impure with one of the primary forms of ritual impurity, and a person touched that hair but did not touch his flesh, the person who touched him is not ritually impure, for this hair is not considered to be a handle to bring in ritual impurity or to remove it.