What are the ramifications of the comparison of "Acheres" to the Meyu'edes?
Kidushin: It teaches us that an Amah Ivriyah can be acquired with Kesef
Who is meant by Acheres?
Oznayim la'Torah (citing one opinion in the Mechilta): Presumably, the Torah is referring to a Bas Yisrael (and not another Amah Ivriyah). 1
Oznayim la'Torah: As implied by the word "Yikach lo"
What is "She'er"?
Rashi (citing the Mechilta), Ramban #1 (in Pasuk 9, citing Targum Onkelos), Rashbam, and Targum Yonasan: Sustenance. 1
Ramban #2 (in Pasuk 9): Proximity of flesh at the time of intimacy. 2
What is "K'sus"?
Rashi (citing the Mechilta), Targum Onkelos and Targum Yonasan: Clothes.
Ramban (on Pasuk 9): Bedding. 1
Like the Pasuk later in 22:26.
What is the meaning of "Onasah Lo Yigra"?
Rashi (citing the Mechilta), Ramban (on Pasuk 9), Rashbam, Targum Onkelos and Targum Yonasan: 'He shall not detract from her designated times of intimacy. 1
Rashbam: He shall not withhold from her a place to live. 2
Nedarim, 15b: It also teaches us that the husband is duty-bound to givr his wife intimacy and that if he makes a Shevu'ah not to do so, the Shevu''ah is invalid. 3
Ramban: The Torah is warning the son here, that in the event that he marries another wife, he may not relegate the Meyu'edes to the status of a concubine, by being intimate with her only casually, clothed and on the floor, whilst he is intimate with his second wife regularly, on a bed and without clothes.
Like the word "Me'onah" (the 'Mem' of which is dispensable [See Rashbam]).
Nedarim (Ibid.): However, if he makes a Neder 'Hana'as Tashmishech alai', the Neder is valid. See Torah Temimah, note 85.
What do we learn from "Im Acheres Yikach lo
Seforno: We learn that a man may not marry more women if he cannot provide his obligations to them. 1
Kidushin 16a: It equates an Amah to an Arusah. Just like a document can be Mekadesh, it can acquire an Amah.
Rashi: If one marries a woman in addition to the Meyu'edes, he must still fulfill his obligations to the Meyu'edes.
Aruch ha'Shulchan (EH 26:8, based on the Rambam): If he is Mekadesh a woman, these obligations come after Nisu'in. However, a Meyu'edes is like a concubine; these obligations do not apply. 2
To whom is "She'erah, K'susah,and Ona'asah" referring?
Mechilta: It is referring to the Bas Yisrael
Mechilta: Because we know the Amah Ivriyah from "ke'Mishpat ha'Banos Ya'aseh lah". See also Torah Temimah, note 86.
What are the ramifications of the comparison of "She'er, K'sus,and Ona'ah"?
Kesuvos, 48a: It teaches us that he must give her clothes a. according to her 'body' ("She'eirah")