A Mishnah discusses a fascinating case (7:6). A mikveh containing exactly forty seah (the minimum volume) is used by one that requires it. As he steps out he will take some of the water with him thereby invalidating the mikveh for anyone that would follow him. A debate ensues in the Mishnah regarding the second person that enters the mikveh as the first person is stepping out. The first opinion is that since he has taken some of the water out with him it is too late for the second person; the mikveh is invalid. R’ Yehuda explains that provided that the first person still has his feet in the mikveh, the mikveh is valid. The water on the body of the first person is still considered connected to and part of the mikveh’s water. How are we to understand the debate? 88
The Mishnah Achrona initially suggests that perhaps the debate could be understood as whether water that flows (ketafres), i.e. down the first person’s body, can be considered attached. He uses this suggestion to explain another potential question. The next Mishnah teaches that if one immerses a bed, and its legs sink into the thick muddy floor, that the immersion is nonetheless valid. One cannot immerse in thick mud and that area should be considered as if it were outside the mikveh. Nonetheless the Mishnah explains that everyone agrees that it is valid as the mikveh water precede the bed legs and surround them as they sink into the mud and that water is considered attached to the mikveh. That case appears similar to our own, yet the Mishnah does not record a debate. He explains that the difference in this case is that water that is surrounding the person is flowing unlike the water that surrounds the bed leg.
The Tosfot (Gittin 16) however question this explanation as a Mishnah in Taharot (8:9) teaches that ketafres is not considered an attachment and this point is not debated. R’ Tam there explains that this case is different in that since the water is destined to fall in the mikveh it is considered attached.89 In other words sometimes ketafres is considered attached and this case is one such instance. According to the Maharik this is indeed the debate in our Mishnah: can water that is flowing but will inevitably land in the mikveh be considered attached now?
Nevertheless the Mishnah Achrona cites the explanation of the Rivash who explains that indeed everyone agrees that ketafres is considered attached. What then is the debate? The Mishnah continues that if a sagos (thick blanket) is immersed in a forty seah mikveh and a person immerses in it as it is being removed, that absorbed water is considered attached to the mikveh. He understands that this is the universal opinion; ketafres in this context is considered attached. But why is this case agreed upon and our earlier case debated? The Rivash explains that the sagos has completely absorbed a great volume of water. In our case, there is only a thin layer of water that covered the first person as he exits the mikveh. Consequently R’ Yehuda and the Chachamim debate whether such a thin layer qualifies as being attached. The Tosfot Yom Tov (3:2) explains in a similar manner that the Chachamim argue that since as the person exists he may be partially dry, the water on his body cannot be considered attached.
The Tifferet Yisrael attempts to answer the earlier question of the Tosfot that it is true that R’ Yehuda agrees with the Mishnah in Taharot that ketafres is not considered attached. Nonetheless, the water in our case is not flowing down a slope – the body is vertical. Consequently we use a different principle of gud achit; we conceptually “pull down” the water and consider it already in the mikveh below.90 Accordingly, as explained by the Bartenura, the case of the sagos cited above must be only according to the opinion of R’ Yehuda. That is because the Chachamim would maintain that neither ketafres nor gud achit could apply in that case.
88 Note that the Gemara (Chagigah 19a) provides two opinions regarding the whether the debate is only regarding one that requires immersion as a stringency or whether it relates to one that definitely requires immersion. This aspect has been neglected in our discussion.
89 See also the answer of the Ri cited in that Tosfot.
90 The term borrowed from, and more familiar in, the law of partitions.
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