Scalls may become unclean for two weeks and by two signs: by thin yellow hair and by spreading. By thin yellow hair: means stunted and short, the words of Rabbi Akiva. Rabbi Yohanan ben Nuri said: even though it is long. Rabbi Yohanan ben Nuri said: what is the meaning of the expression when people say, "This stick is thin," or "This reed is thin"? Does "thin" imply that it is stunted and short and not stunted and long? Rabbi Akiva replied: before we learn from the reed let us learn from hair, [for they say] "So and so's hair is thin": "thin" means that it is stunted and short and not stunted and long.

[Black hair] that sprouts up affords protection against yellow hair and against a spreading, whether it was clustered together or dispersed, whether it was encompassed or unencompassed. And that which is left [over from before the scall] affords protection against yellow hair and against a spreading, whether it is clustered together or dispersed, and also when encompassed, but it affords no protection where it is at the side unless it is distant from the standing hair by the place of two hairs. If one hair was yellow and the other black, or if one was yellow and the other white, they afford no protection.

Yellow hair that preceded a scall is clean. Rabbi Judah says that it is unclean. Rabbi Eliezer ben Jacob says: it neither causes uncleanness nor does it afford protection. Rabbi Shimon says: anything in a scall that is not a sign of uncleanness is a sign of cleanness.

How does one shave who has a scall? He shaves outside it and leaves next to it two hairs in order to determine whether it spreads. If he was certified unclean on account of yellow hair, and then the yellow hair disappeared and other yellow hair appeared, and so also if there was a spreading, irrespective of whether the certification took place at the beginning, at the end of the first week, at the end of the second week or after his release from uncleanness, behold he remains as he was before. If he was certified unclean on account of a spreading, and the spreading disappeared and then reappeared, and so also if there was yellow hair, irrespective of whether the certification took place at the end of the first week, at the end of the second week or after his release from uncleanness, he remains as he was before.

Two scalls side by side and a line of hair separating between them: If a gap opened up in one place he is unclean, But if it opened up in two places he is clean. How big should the gap be? The space of two hairs. If there was a gap in one place, even though it is as big as a split bean, he is unclean.

Two scalls one within the other and a line of hair separating between them: If there appeared a gap in one place the inner one is unclean, But if in two places it is clean. How big must the gap be? The space of two hairs. If there was a gap in one place of the size of a split bean he is clean.

One who has a scall with yellow hair within it is unclean. If subsequently black hair grew in it, he is clean; even if the black hair disappeared again he remains clean. Rabbi Shimon ben Judah says in the name of Rabbi Shimon: any scall that has once been pronounced clean can never again be unclean. Rabbi Shimon says: any yellow hair that has once been pronounced clean can never again be unclean.

If one had a scall the size of a split bean and it spread over all his head he becomes clean. The head and the beard do not prevent [one another], the words of Rabbi Judah. Rabbi Shimon says: they do prevent. Rabbi Shimon said: Is there not a logical inference: if the skin of the face and the skin of the body, between which something intervenes, do prevent [one another], the head and the beard, between which nothing intervenes, should they not also prevent [one another]? The head and the beard do not combine, nor is a spreading from one to the other effective. What exactly counts as the beard? From the joint of the jaw to the thyroid cartilage.

Scalp baldness (karahat) or forehead baldness (gabahat) may become unclean in two weeks and by two signs: by quick flesh or by spreading. What constitutes baldness? If one ate neshem or smeared himself with neshem or had a wound from which hair can no longer grow. What is the extent of scalp baldness? From the crown sloping backwards to the protruding cartilage of the neck. What is the extent of forehead baldness? From the crown sloping forwards to the region facing the hair above. Scalp baldness and forehead baldness cannot be combined, nor is spreading from one to the other effective. Rabbi Judah says: if there is hair between them they cannot be combined, but if there is none they must be combined.