I realize this is a fundamental aspect of Judaism and I know that the menstruation + 7 days rule is straight from Leviticus, I'm just curious what the source is in the Oral/Written Law for the mikvah's role in completing niddah and restoring family purity.

My friend is wondering whether this is actually part of the Written/Oral Torah or if it is something that rabbis subsequently interpreted as a requirement. I realize that there are archeological records of mikvahs that pre-date the codification of the Oral Law, but I do not have enough Torah knowledge to be able to point to the specific passages in the Oral/Written Law where it specifically mentions the necessity of immersing in a mikvah at the end of the niddah period.

  • Somewhat tangential, but you should be aware that the biblically-mandated requirement from Leviticus for a niddah (as opposed to a zavah) is to immerse at the end of seven days from the start of her period
    – Joel K
    Jan 25, 2021 at 19:48
  • 1
    Relevant: judaism.stackexchange.com/questions/93059/…
    – Joel K
    Jan 25, 2021 at 19:49
  • @JoelK very helpful, thanks! Jan 25, 2021 at 20:03

1 Answer 1


Beit Yosef (Yoreh Deah 197:1) cites several sources:

  1. (Rambam, Hil. Issurei Biah 4:3, ultimately from Sifra, a Tannaitic midrash on Leviticus:) Via a binyan av (generalization) from Lev. 15:18, which says that people impure because of having relations have to "bathe in water"; we derive from this that immersion is (for all impure people) an essential part of the purification process.

  2. (R. Akiva in Talmud, Shabbat 64b:) From Lev. 15:19, תהיה בנדתה, "she shall remain in her niddah status" (beyond the time when she has her actual flow), until she immerses in a mikvah. (Apparently the Beit Yosef had a different version of this Gemara, since our texts instead have R. Akiva deriving this from 15:33, והדוה בנדתה, "she who is ill with her niddah status.")

  3. (Rav Hai Gaon:) Via a kal vachomer (fortiori argument): if one who touches a niddah's bed needs to immerse in order to become pure (Lev. 15:21), certainly the niddah herself needs to.

  4. (Rabbeinu Yaakov:) In connection with the spoils from the war against Midian, the Torah states (Num. 31:23) that they have to be purified with מי נדה. The Talmud (Avodah Zarah 75b) states that this means "water in which a niddah has to immerse" - i.e., a mikvah. Zechariah 13:1 also speaks of "a water source... for a niddah" (implying that she has to immerse in one).

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