Negaim, Chapter 4, Mishnah 11. Our mishnah continues the perek's discussion of a baheres that has spread while the original body of the nega, the om, has disappeared. It then turns to a second subject: a baheres that reaches the required size of a gris only in stages, and white hairs that were already in place before the full gris of baheres existed.
A siman tumah that appears in the spread
Our mishnah opens with "Baheres kagris, u'posasoh kagris": a nega that measured one gris, and then an additional gris's worth of baheres was added to it. Growth like that is a pissayon in every sense. Should it happen while the man is sitting in hesger, whether in his first seven days or in his second, the spreading by itself is a sufficient siman tumah for the kohen to pronounce him muchlat. And if it surfaced only after petur, once he had already been sent home tohor, spreading at that stage carries tumah with it as well.
Now comes the complication: "nolad lapissayon michyah" or two white hairs. Within the newly spread area a michyah, a patch of healthy flesh, appeared, or seir lovon, two white hairs, developed there. And then, "veholach lo ha'om": after the hachlatoh, the original om departed and vanished.
Rebbi Akiva declares him tomei. The Rav explains his position: "yeish kan nega vesiman tumah imo," there is a nega here and a siman tumah together with it. Even though the om is gone, the area of the spread carries a michyah or two white hairs, it is a direct continuation of the earlier nega, and the tumah of hachlatoh stands.
The Chachamim rule "teiraeh bis'chilah." To their mind, once the om has vanished there is nothing left for the pissayon to attach itself to, and the added area forfeits its status as an outgrowth of anything. What does remain is a patch that now holds a michyah or seir lovon, and that qualifies as a fresh nega, tomei on its own account, examined as though it had just made its appearance.
The Rav points out that even according to the Chachamim the man is tomei immediately: the pissayon had already rendered him tomei when the kohen looked at him, and a michyah or seir lovon are themselves simanei tumah that render a nega tomei from the very beginning. So what turns on the dispute? The nafka mina lies in the korbanos. According to Rebbi Akiva this is all one nega, one continuous tumah, and when the man becomes tohor he brings a single korban. According to the Chachamim, who count the michyah or the white hairs in the spread as a second, independent nega, the man must bring a second korban when he becomes tohor from it. In this respect the Chachamim are the stricter opinion.
That very same logic also produces a kula for the Chachamim, precisely as we find in the case of a nega coming before the kohen for the very first time: should this nega present itself on Chol HaMoed, or within a chosson's shivas yemei mishteh, there is no obligation to bring it for inspection just then. Since in their view the matter begins afresh, "teiraeh bis'chilah," the viewing is allowed to wait.
White hairs that came before the full gris of baheres
The mishnah now turns to a series of cases built on a fundamental rule: the baheres must precede the white hairs. Two white hairs are a siman tumah only when the nega turned them white, when a full baheres of a gris was already present and its power converted black hairs into white ones. Each case that follows is a variation on this theme.
Case one: "Baheres kachatzi gris vein bo klum." A patch of baheres measuring only half a gris, too small to be a nega at all, and inside it there is nothing whatsoever, not one white hair. Then, "nolad baheres kachatzi gris," a second half-gris of baheres formed alongside it, "u'vo sa'arah achas," and this one does contain a single white hair. The ruling: "harei zu lehaskir." A complete gris of baheres is now present and must be shut away for a seven-day observation; but one hair does not amount to a siman tumah, so what will come of it is left for the week ahead to reveal.
The chiddush here seems to lie in the joining itself: these two halves combine with one another to form the required gris even though they did not form at the same time. For the ruling of hesger alone the mishnah could have taught something stronger, since even a whole gris of baheres with one white hair in it is not grounds for hachlatoh, two hairs being required, and the same din of hesger would apply. So the point being made is that there is a tzeiruf between the two halves that arose one after the other.
The second case: "Baheres kachatzi gris," half a gris of baheres, "u'vo sa'arah achas," with one white hair inside it; afterwards, "venolad baheres kachatzi gris," a further half-gris arose, and it too has "sa'arah achas," a lone white hair. The verdict here is again "harei zu lehaskir." Count what stands before us: a full gris of baheres, together with two white hairs, a combination that would ordinarily yield hachlatoh. The difficulty is the sequence. The first hair whitened at a time when no gris of baheres yet existed, so as far as that hair goes the baheres came second rather than first. Only later did the additional half arrive to complete the measure, bringing its own hair along with it. He is consequently not declared muchlat, but shut in for seven days while the nega is watched.
The third case: "Baheres kachatzi gris," half a gris, "u'vo shtei se'aros," and this patch contains two white hairs; then, "venolad baheres kachatzi gris," another half-gris formed beside it, holding one white hair. Once more, "harei zu lehaskir." The pair of hairs whitened before any full gris of baheres was in existence, so they are disqualified from serving as simanei tumah, and the solitary hair in the newly formed half cannot combine with them to change the picture. Hesger it is.
The thread running through these final cases is one and the same: in each of them the white hairs, either both of them or one of them, were already there before a full baheres kagris existed. The Torah's term is hafakh, a language of turning over and changing: the nega must turn black hairs white. That transformation is what demonstrates that this is truly a nega, its potency shown precisely by its ability to convert black hair into white. Where the hairs came first, that demonstration is missing, and the person is placed in hesger rather than declared muchlat.