Having taught us the Azharah against Achos Av and Achos Eim in Acharei-Mos - 18:13, why does the Torah repeat it here?
Rashi: To teach us that one is Chayav on both the sister of one's father and of one's mother, whether she is a paternal sister or a maternal sister. 1
Rashi (Ibid.): As opposed to the Isur of one's uncle's wife (in the following Pasuk), which is confined to the wife of his father's paternal brother.
Having taught us the Din of Ha'arah regarding Nidah (in Pasuk 18), why does the Torah see fit to repeat it here?
Sanhedrin, 55a: To teach us (Im Eino Inyan) that the Isur Ha'ara'ah extends even to bestiality. 1
Refer to 20:13:1.1:1.
Why is the punishment for an aunt left vague ("Avonam Yisa'u"), and there is no Pasuk at all regarding the punishment for Achos Ishto, as there is for all other Arayos?
Riva (in Pasuk 10, citing Ibn Ezra and R"M of Kutzi) and Moshav Zekenim (18:25): Moshe did not want to write them, 1 in deference to his father Amram 2 , who married his father's sister 3 , and the honor of Ya'akov Avinu, who married two sisters. And since he did not write about a father's sister, he also omitted a mother's sister. 4
Though in fact, based on the Hekesh to Nidah - in Acharei-Mos, 18:29, all the Arayos are subject to Kareis.
Moshav Zekenim: Moshe taught all the Arayos to the Nesi'im and the Zekenim briefly (bccause it is forbidden to teach Arayos to three people - Chagigah 2:1), and they taught Yisrael - everyone taught at most two Talmidim at a time. Moshav Zekenim also asked why the Torah omitted "Ish", which it says about all other Arayos. Perhaps it is to avoid calling attention to Amram, who is called "Ish" - in Sh'mos 2:1 (PF)
Sifsei Chachamim (in Sh'mos 6:20): The Pasuk calls Yocheved, who was Amram's father's sister "Dodaso", wheres in Parshas Arayos, "Dodaso" means the wife of one's uncle.
The Torah could have taught a punishment for the mother's sister alone, just like a separate Pasuk forbids her -18:13 (PF)
