Mikvaos, Chapter 8, Mishnah 2. This mishnah deals with the tumah of a baal keri. Alongside the Torah's own law of tumas keri, Chazal added a category of their own: a person who was not motzi zera, who had no emission that would render him tamei mi'de'oraisa, may still be treated as tamei mi'drabbanan. The concern is that in the course of urination there could be some trace of keri mixed in, a residue that would not be visible on its own, and out of that suspicion the Chachamim ruled him tamei with regard to eating terumah.
A bit of background will make the mishnah's language clear. A baal keri carries the status of a rishon letumah. Min haTorah, there are four ways in which this tumah can take hold of a person:
- A discharge of keri from his own body.
- Touching keri, which brings a person into this tumah as well.
- Relations with a woman: both of them become tamei, and he is a baal keri even though the emission was entirely beis hastarim, concealed within her body. She too is tamei, despite the fact that the contact was internal, in a concealed place.
- A woman who has a discharge after relations, within the span of time in which the zera is still viable. Exactly how long that span lasts is a machlokes tana'im that we will meet in the next mishnah.
All four of those are Torah tumah. Our mishnah, by contrast, is dealing with the rabbinic layer.
The mishnah opens: "Eilu baalei keryin shehein tzrichim tevilah", these are the ones who are considered baalei keri and therefore need a tevilah, purely because Chazal declared them tamei. The case is a man who notices something unusual as he urinates.
"Ra'ah mayim chalukim", he saw water that was off in its color, or that did not emerge in the ordinary manner, not in a steady stream as urine normally comes out. "O achurim", or the fluid was cloudy and darkened. In these cases the ruling depends on when in the process it happened.
"Bitchilah tahor": should the irregularity show itself in the opening moments, we disregard it and raise no suspicion of keri at all, since restraining oneself beforehand is itself enough to affect the color and the manner in which the first drops emerge. "Be'emtza o besof tamei": but if the flow started out normally and only later, partway through or toward the finish, did it turn discolored or come out irregularly, he is tamei. Here too the ruling rests on nothing more than a rabbinic chumra, with no Torah tumah involved at all.
The mishnah then adds a further case: "mitechilah ve'ad sof", if from beginning to end the entire urination was abnormal, either that he was only able to pass it in drops rather than in a stream, or that it was bemar'eh acher, an altogether different color throughout, he is tahor. When the abnormality is uniform from start to finish, it points to a physical condition rather than to keri mixed in partway through.
Now the mishnah turns to a different appearance: "levanim venimshachim", white and viscous, drawn out and mucous-like. Here the Tanna Kamma holds tamei. Even though it did not emerge beko'ach, with force, and mi'de'oraisa tumas keri applies only when it comes out yoreh kachetz, shot out like an arrow, nevertheless, since the substance itself resembles keri, Chazal imposed their injunction and declared him tamei.
Rebbi Yose disagrees: "levanim kachurim". Since it did not emerge with force the way genuine keri does, white and viscous fluid is governed by exactly the same rule as darkened, cloudy fluid. In other words, it falls back into the distinction the Tanna Kamma drew earlier: if it appeared at the very beginning, he is tahor, and if it appeared at the end, he is tamei.
So this mishnah gives us a careful set of markers. Chazal are not creating a new Torah tumah; they are reading the signs of urination and asking whether an unnoticed trace of keri might plausibly have been carried along with it, and they rule tahor or tamei accordingly.