Why does the Torah add a 'Vav' in "ve'Ishah"?
Rashi (in Shabbos, 16b): To incorporate a Ketanah on the day that she is born in the Din of Nidus.
From where must the blood flow in order to render the woman Tamei?
Rashi: We learn from "ve'Hi Gilsah Es Mekor Damehah" (Vayikra 20:18) that only blood that flows from the womb renders her Tamei. 1
See Torah Temimah, note 73. and in Vayikra chap. 20, note 47.
Why does the Pasuk add the phrase "Dam Yih'yeh Zovah bi'Vesarah"?
Rashi #1 and Rashbam: To teach us that it is only red (blood) that is Metamei (but not if it is white, like the Zov of a Zav
Why does the Torah insert the (otherwise superfluous) word "Yih'yeh"?
Nidah, 54: To teach us that the blood of Nidus is Metamei even after it has dried. 1
Nidah, 41b: to teach us that if a woman exudes her husband's Zera, she is Tamei.
See Torah Temimah, note 74.
What are the implications of the word "Dam Yih'yeh Zovah bi'Vesarah"?
Nidah, 21b: It implies that the woman is only Tamei if the blood appears on her flesh, 1 but if it appears in a tube that she placed inside her womb, in the sac of a foetus or if it appears in a piece of flesh, 2 she is Tahor.
What are the connotations of the word 'Nidah'?
Rashi: She is so-called because she is driven away (banished) from touching all people. 1
As in Iyov, 18:18 (Rashi).
What are the implications of Shiv'as Yamim Tih'yeh be'Nidasah"?
Pesachim, 90b: It implies that a Nidah is Tamei for the full seven days and that she cannot Tovel until nightfall of the eighth day. 1
Refer to 15:19:4:1*.
Sifra: It includes the nights.
Sifra: It implies that the seven days must be consecutive. 2
How many sightings must she have in order to be Tamei for seven days?
Rashi: Even if she sees only once she is Tamei for seven days. 1
The Sifra learns this from the fact that the Torah writes "Tih'yeh be'Nidasah" implying even if she doe not see blood throughout the seven days. See Torah Temimah. note 83..
Seeing as the next Pasuk teaches us that the Mishkav and Moshav of a Nidah are Metamei, why does the Torah need to teach us that she is Metamei?
Sifra: To teach us that whoever touches her is a Rishon le'Tum'ah and is only Metame food and drink, but not Adam or Keilim.
Why does the Torah not obligate a Nidah to bring a Korban like a Zavah?
Ramban (on Pasuk 11): Because Nidus is a natural phenomenon. As opposed to a Zavah, it terminates naturally and she is not healed from an illness.
Why does the forbid a Nidah, who has done nothing wrong, on a her husbaand for seven days?
Nidah, 31b: Based on the principle 'Familiarity breeds contempt!' the Torah figured that, if a woman is separated from her husband for seven days (each month), she will remain dear to him.
The Torah does not say how a Nidah becomes Tahor?
Da'as Zekenim, from Avodah Zarah 75b): "B'Mei Nidah" (in Bamidbar 31:23) hints that a Nidah immerses in a Mikveh [after the seven days].
