Mikvaos, Chapter 2, Mishnah 10. Our mishnah turns to a mikveh that contains a slurry, a mixture of earth and water blended together into something between mud and cement. The question is when such a mixture still carries the halachic status of water, so that it counts toward the mikveh and one may even immerse in it, and when it has lost that status.
The dispute
The mishnah's case is a pool "sheyesh bo arba'im se'ah", containing forty se'ah, except that the measure is reached only by combining the two components mentioned, "mayim v'tit", water and mud; neither element alone amounts to the required quantity. On this Rebbi Eliezer holds "matbilin b'mayim", the immersion takes place in the water, "v'ein matbilin b'tit", and not in the muddy part. In his view a person has to be able to submerge himself within the watery portion by itself, separate from the earth. Rebbi Yehoshua's ruling is "b'mayim u'v'tit", both in the water and in the mud. His logic: if the mud is good enough to be reckoned into the forty se'ah, it is equally good enough for the body to be submerged in it.
Which mud is this?
The mishnah immediately narrows the case: "B'eizeh tit matbilin?", in what sort of mud may one immerse? "B'tit shehamayim tzafin al gabav", mud over which the water floats. Rebbi Yehoshua's leniency applies only to a loose mixture, mostly water, not tightly packed, with water still resting on its surface.
The next clause draws a limit. Where the liquid has drifted to one end of the pool while the earth has sunk to the other, the two are no longer a single blended mass; the mishnah describes this as "hayah hamayim mitzad echad", the water being on one side. In that situation, says the mishnah, "modeh Rebbi Yehoshua", Rebbi Yehoshua grants the point: "shematbilin b'mayim v'ein matbilin b'tit", immersion is valid in the water and invalid in the mud.
How loose must the mud be?
The mishnah then refines the definition further: "V'eizeh tit amru?", what kind of mud were they speaking of?
- The first standard given is that of Rebbi Meir: "b'tit shehakaneh yored mei'eilav", mud in which a reed goes down of its own accord. Set a stick upright into the mixture, and if it works its way through until it reaches the floor of the pool, we see that nothing here is packed or condensed; the substance keeps the halachic character of water.
- A less demanding measure is offered by Rebbi Yehudah: "makom she'ein hakaneh omed", a spot where a reed will not remain upright. He does not insist, as the previous opinion does, that the stick travel all the way through the mixture. Plant a stick into normal ground and it stays put; here it is sufficient that the substance cannot hold the stick in place, so that it topples rather than standing, even if it never reaches the bottom.
- More lenient again is Abba Elozor ben Delo'i, whose test is "makom shehamashkoiles yoredes", a spot where the plumb weight goes down. Builders would suspend a weight on a cord to verify that a wall was true. Let such a weight be dropped in, and if it works its way through the mixture that is enough, notwithstanding that a weight of that sort would penetrate substances considerably denser than water. A mixture like this is not called mud at all, but water.
- Rebbi Eliezer takes the barrel as his gauge: anything "hayored b'fi chavis", which runs out through a barrel's mouth. Should the mixture be pourable through that opening, its consistency is loose enough.
- For Rebbi Shimon the test is "hanichnas b'shefares hanod", whatever goes through the little spout of a skin flask, the narrow opening from which its contents are released. That degree of flow already suffices.
- Finally comes the yardstick of Rebbi Elozor b'Rebbi Tzadok: "hanimdad balog", whatever admits of being measured in a log, the vessel used for measuring liquids. If the mixture can be taken up in that cup and poured off, the requirement is met; and because the log's mouth is broader than the openings mentioned before, a somewhat denser mixture will qualify. It is treated as a liquid, and immersion in mud of that kind is valid.