Having already stated "ve'He'emidah lifnei Hashem" in Pasuk 16, why does the Torah repeat it?
Rashi: This is part of a strategy which included moving her around from one location to another, to encourage her to confess her guilt, 1 by tiring her out and causing her to become confused.
Rashi: In order to avoid needlessly erasing the holy Name of Hashem.
What is the meaning of "u'Fara Es Rosh ha'Ishah"?
Rashi #1 (citing the Sifri) and Targum Yonasan: It means that the Kohen unties 1 her plaits 2 in order to embarrass her. And we learn from here that it is a disgrace for B'nos Yisrael to expose their hair. 3
Rashi #2 (in Sh'mos 32:25): It means to uncover or to reveal.
What exactly, does "Lifnei Hashem" mean?
Rashi: It means next to the Nikanor 1 gate, which is the eastern gate leading from the Ezras Nashim to the Ezras Yisrael and the Ezras Kohanim.
Why does the Kohen now place the Minchah into the hands of the Sotah?
Why is the Mei Sotah called 'bitter water'?
Rashi (from the Sifri): Because when she drinks it, it will become bitter for her. 1
Ramban (citing Sotah, 20a): The Kohen actually places something bitter into the water 2 in order to arouse her to admit her guilt in the event that she is guilty.
Ramban (citing the Sifri): When the Kohen places the Parshah of Sotah into the water, the water turns bitter.
Ramban: When the Sotah drinks the water, it tastes sweet like any other water. However, if she is guilty, the moment it enters her stomach, she feels a bitter taste in her mouth and in her stomach, like someone who imbibes something that makes him feel that he wants to vomit.
What is the translation of "Mei ha'Marim"?
Ramban, Targum Onkelos and Targum Yonasan: It means 'the bitter water'. 1
Ramban: And not the water of bitterness, as the Ibn Ezra translates it (See Ramban, DH 've'Amru').
What is the definition of "ha'Me'arerim," bearing in mind that the water is holy water from the Kiyor?
Rashi #1 (citing Targum Onkelos): It means water that diminishes her from the world. 1
Rashi #2 and Ramban: It means water that brings a curse on her body. 2
Targum Yonasan: It means water that examines her. 3
Rashi learns from "u'Para Es Rosh ha'Ishah" that he unbraids her hair. In Shemos (32:25), he said that Pri'ah is uncovering!
Mizrachi: Here, we expound ha'Ishah (it could have said Roshah; Gur Aryeh - we expound "Es") to teach added exposure (unbraiding), just like it teaches that he exposes her body.
Malbim (56): Pri'ah in a man is exposure. For an Ishah, it is Binyan to braid her hair (like Hashem did for Chavah - Brachos 61a); Pri'ah is unbraiding it.
Why does he expose her head?
Moshav Zekeinim (from Sotah 7b): She exposed her head and body for the Bo'el, so this is done to her.
Rosh (12): This is Midah k'Neged Midah. She spread nice cloths on her head, so the Kohen removes her hat and puts it under his foot. She braided her hair for him, so the Kohen unbraids it. 1
Rosh: She beautified herself for Aveirah, so Hashem makes her repulsive. She stood at her doorway, so she is stood up in Sha'ar Nikanor, and shows her disgrace to all. She adorned her face for him, so her face turns yellow. She painted her eyes for him, so they bulge out. She gestured with her fingers, so her fingernails fall out. She girded a Mitzri belt, so a Mitzri rope is tied above her breasts. She fed him dainties, so her Korban is animal food. She sinned covertly, Hashem exposes her in public.
QUESTIONS ON RASHI
Rashi writes that he unties her braids... an exposed head is disgraceful for married women. Untied braids is unlike an exposed head!
Moshav Zekeinim: If untying her braids is disgraceful, all the more so if the entire head is exposed!
Ha'Kesav veha'Kabalah: Pri'ah is when hair rests on her shoulders. For this he must also unbraid her hair.
He also exposes her head. Refer to 5:18:152:1.