Halakhah su Levitico 11:36

In the last chapter, we distinguished between the two bodies of water that purify, a ma’ayan (natural spring) and a mikvah (collection of rainwater). The Sifra (commenting on Vayikra 11:36) draws a parallel between them, teaching that just as God creates ma’ayanot naturally, without human intervention, so, too, must the water in a mikvah reach it without passing through receptacles.¹Conceptually, passing through man-made receptacles indicates human intervention, as opposed to a natural process directed by God. However, the Sifra does provide one exception. If no human indicated any interest in water passing through the receptacle, then the water remains acceptable for mikvah use. For example, if someone places his pot outside to dry in the sun, and then rain falls unexpectedly, whatever rainwater collects in the pot does not automatically become she’uvim, as the pot’s owner - seeking to dry his pots in the sun - clearly does not desire the water. However, if the owner, upon realizing that his pot contains water, lifts the pot to use its water, then the water becomes she’uvim. Thus, in order to use the water for a mikvah, the owner must knock over the pot without lifting it, allowing the water to continue its natural flow without human redirection. Moreover, had the owner initially placed the pot outside for the purpose of collecting rainwater, then the water would become she’uvim the moment it enters the pot - even if the owner promptly knocks the pot over - because the pot received the water as a result of deliberate human actions (see Mishnah, Mikva’ot 4:1). If, for example, one drew water from a well with a bucket and then poured the water into a pit, the water would be considered mayim she’uvim (drawn water) and would hence be disqualified for use in a mikvah. In the modern context, water from the tap constitutes mayim she’uvim because it passes through receptacles in purification plants and water meters.²Rav Moshe Heinemann explained this fact in a lecture to the Council of Young Israel Rabbis. In previous generations, the Aruch Hashulchan (Yoreh Deah 201:169) and Rav Moshe Feinstein (cited in Taharat Hamayim, Chapters 40-42) actually permitted building mikva’ot with tap water under extremely dire circumstances, but Rav Yirmiyah Katz (Mikveh Mayim, vol. 3 pp. 93-95) argues that water today passes through many places between the reservoir and the faucet that did not exist a couple of generations ago, so nobody would permit using tap water nowadays. Indeed, Rav Moshe himself writes that tap water should generally be presumed to be unacceptable for mikva’ot (Teshuvot Igrot Moshe, Y.D. 3:63).

The Torah (Vayikra 11:36) states, “A ma’ayan (natural spring) or bor (cistern), a gathering of water, shall be pure.” The Torah mentions two bodies of water, a ma’ayan and a bor, neither of which can become tamei (ritually impure). The Sifra, commenting on this verse, understands that they cannot become tamei because they are themselves sources of purity. Hence, besides their own inability to become tamei, immersion in them purifies people and utensils that were tamei.

On the other hand, the Rambam (Hilchot Mikva’ot 4:1-2) and Ri (cited in Tosafot, ibid.) claim that the entire problem of mayim she’uvim exists only on a rabbinic level, while the Torah itself even permits a mikvah comprised entirely of mayim she’uvim. Although the Sifra derives the concept of she’uvim from a verse in the Torah (Vayikra 11:36), the Rambam believes that the Sifra merely intends that the Rabbis saw an allusion (asmachta) in the Torah to their enactment. The Aruch Hashulchan (Y.D. 201:11-17) reviews two additional opinions that appear in the Rishonim.