What is the significance of the fact that Esav married Yishmael's daughter?
Bava Kama 92b: The fact that Esav ha'Rasha married the wicked Machalas is the source of the saying ,'The poor-quality date-palm went across to join forces with the barren tree.' 1
Oznayim la'Torah: When he saw that Yitzchak blessed Yaakov with children, he understood why. This made him jealous of Yaakov and prompted him to improve his ways - so he married his uncle Yishmael's daughter. 2
What is the significance of the name Machalas, whose real name was Bosmas (See Targum Yonasan)?
Rashi (in 36:3): Because ?Machalas? stems from ?Mochel? (forgive), and one of three people 1 whose sins are forgiven is a Chasan on the day of his wedding. 2
Yerushalmi (Bikurim, 3:3): The other two are a Ger who converts, and someone who is elevated to a high position - such as a king or a Rosh Yeshivah.
What is the significance of the fact that Machalas was the sister of Nevayos?
Rashi : To teach us that Yishmael died then, and her brother Nevayos married her off in his place. 1
Rashbam: Because he was the oldest brother. 2
Malbim: Because Nevayos was a Rasha, and children generally are like the mother's brother - even so, he married Nevayos' sister.
Rashi: From this we learn that Ya?akov was sixty-three at that time, fourteen years before he arrived in Charan ? a proof that he spent fourteen years in the Yeshiva of Eiver. See Rashi.
And it is the way of the Torah to point this out - as we find by Miriam, whom the Torah calls "Achos Aharon" (Sh?mos 15:20) because he was the older of Miriam's brothers) and "va'Achos Lotan Timna" (36:22), because Lotan was Timna's oldest brother.
Why does the Torah add the (otherwise superfluous) words "Al Nashav"?
Rashi: To teach us that he added evil to evil, by not divorcing his Cana?ani wives.
Why is there a Pesik (a line, signifying a break in the Pasuk) after "Machalas"? And why must the Torah say that Yishmael was Ben Avraham?
Ha'amek Davar citing a Midrash: This teaches that he went to Yishmael to entice him to kill Yitzchak (refer to 27:41:2:2). Yishmael died, and Esav repented and married Machalas, for she was Avraham's granddaughter. The Pesik shows that it was unlike he had initially intended.
Why does it say "Lo l'Ishah"?
Ha'amek Davar: He trained her to go in the ways of his house, that she should help him. He thought that this will appease his parents.
QUESTIONS ON RASHI
Rashi writes: "'Sister of Nevayos' - We derive that Yishmael passed away after her betrothal...." But perhaps the verse merely teaches us which wife of Yishmael was her mother?
Gur Aryeh: Even if Machalas and Nevayos shared the same mother, we would still have no idea who that mother was!
Rashi writes: "Yishmael passed away after her betrothal but before her marriage(Nisu'in), and her brother Nevayos married her off." But perhaps a long time elapsed between the betrothal and marriage; in which case we can no longer calculate Yaakov's age when he received the blessings?
Gur Aryeh #1: Esav surely married Machalas immediately, because his intent was to show his father that he had married a worthy woman.
Gur Aryeh #2: Even for a Besulah, Nisu'in is postponed for twelve months at most.
