Why does the Torah see fit to mention that all the current events occurred "while Yisrael was dwelling in that land"?
Rashi: To teach us that all these troubles befell him 1 before he arrived in his father's house - because he delayed his home-coming. 2
Malbim: The the episode with Reuven came because of how he dwelled, i.e. his tent was near Bilhah's tent.
Ha'amek Davar: Because he was steeped in Divine matters and separated from worldly matters (like Yisrael), this happened. Had he been at the level of Yaakov, it would not have occurred.
See Sifsei Chachamim. Gur Aryeh - Why does the Pasuk emphasize that this event took place in "that land" - was the land somehow the cause of this act? Rashi therefore explains that these misfortunes occurred because Yaakov tarried on the road home.
Oznayim la'Torah: It is the trouble with Reuven exclusively that occurred - 'Midah k'Neged Midah' - because he did not honor his father by returning home as quickly as possible. The troubles that occurred earlier were due to his failure to fulfill his Neder - in spite of the fact that the Sifsei Chachamim writes here "Ira lo Kol Zos!"
Why did Yaakov delay his homecoming?
Oznayim la'Torah (to 35:27): Because Esav was still living at home 1 and he was afraid to move in together with him.
Oznayim la'Torah, citing Pirkei d'R. Eliezer.
What was Reuven's sin?
Rashi: He didn't actually sin! 1 What he did was to take the bed of Yaakov (which Yaakov had placed in Bilhah's tent following the death of Rachel) and move it to the tent of his mother 2 Leah. 3
Moshav Zekenim #1: Reuven went away, because Yaakov laid with Bilhah (i.e. made her his primary wife). Yaakov heard that Reuven protested the insult to his mother, and sent for him to return, and then Bnei Yaakov were 12 again. 4
Moshav Zekenim #2: Reuven slept in Bilhah's bed many nights, lest Yaakov sleep with her, but he never sinned with her.
Peninim mi'Shulchan ha'Gra: Reuven went in the house (i.e. tent) when Yaakov was intimate with Bilhah. Yaakov heard, and separated immediately. He would have fathered a 13th son; 5 due to Reuven, he did not. This is why the verse concludes "the sons of Yaakov were 12." We do not translate this verse (during Kri'as ha'Torah), because [the Targum connotes that Reuven sinned, 6 and] anyone who says that he sinned, he errs (Shabbos 55b).
Targum Yonasan: He upset Bilhah's bed, which [Yaakov] used to arrange opposite 7 Leah's, and it was considered as if he slept with Bilhah.
R. Yehoshua (Shabbos 55b): He had Zenus with Bilhah. 8
Ha'amek Davar: He guarded that Yaakov not be able to go to Bilhah's room.
Rashi: He said, 'If my mother's sister was my mother's rival, will my mother's sister's maidservant be my mother's rival?!'
Da'as Zekenim, Hadar Zekenim - "va'Yishkav" is an expression of uprooting (displacing).
According to this, what does Yaakov mean by "you profaned my bed" (Bereishis 49:4)? Perhaps Reuven considered Yaakov's intimacy like that of ordinary people, and really it was Ma'aseh Merkavah. (PF)
It was already prophesied that he will have 12 sons! Perhaps that was due to this episode. (PF)
Targum Onkelos (the concubine of his father) is just like the verse itself! The Targum is based on R. Eliezer and R. Yehoshua (Megilah 3a); they hold that he truly sinned (refer to 35:22:2:6 and the note there); we do not hold like them. People realize that sometimes verses are unlike the simple reading, but when the Targum is like the simple reading, they are sure that it is true. (PF)
Why would this bother Reuven? Surely they were in different tents! Perhaps it means that he was as frequent with Bilhah as with Leah. (PF)
It seems that R. Eliezer agrees; most Tana'im there explicitly disagree. Here, Bilhah is called Pilegesh Aviv. Surely Reuven held that she is a Pilegesh, without Kidushin, and he does not expound "Kenaf Aviv" (Devarim 23:1) like R. Yehudah, so there is no Isur Ervah. Tosfos (to Gitin 6b DH Zevuv) says that it is not common to keep a Pilegesh after Zenus. This implies that there is no Isur. There was however insult to Yaakov; Reuven did so for his mother's honor. (PF)
Why was it so terrible that Reuven mixed into the arrangements of his father's bed? Yaakov could simply return it back to its place!
Maharal (Chidushei Agados Vol. 1, p. 33, to Shabbos 55b): Reuven lay in Yaakov's bed in a manner that made it appear that he had lain with her, such that he would now have to separate from her (see Yevamos 24b).
Why does the Torah refer to Bilhah here as "the concubine of his father"?
Refer to 30:4:151:1.
Why does it say, "va'Yishma Yisrael"?
Seforno: The Torah is telling us that Yaakov knew what Reuven did, yet he did not punish him because he was certain that he immediately did Teshuvah.
Rashbam: It is important to know that Yaakov knew what Reuven did; otherwise we would not understand how, later, he could rebuke him, "Pachaz ka'Mayim..." (49:4). 1
Alshich: Reuven had protested over his mother's honor; that Leah should now be Yaakov's primary wife, and not Bilhah. Yaakov accepted Reuven's point, and acceded to his wish.
Refer to 35:22:6:4*.
Refer to 35:22:6:5.
Ha'amek Davar: Because he heard when he was at the level of Yisrael, via Ru'ach ha'Kodesh, Reuven was not rejected, and there were 12 Bnei Yaakov. Had he heard when he was at the level of Yaakov, Reuven would have been rejected.
What is the significance of the phrase, "And Bnei Yaakov were 12"?
Rashi #1 and Rashbam: With reference to the previous context, now that Binyamin was born, the sons of Yaakov numbered 12.
Rashi #2: This teaches us that Reuven was not guilty of the sin the Torah describes, and that all of Yaakov's 12 sons were Tzadikim. 1 Refer to 35:22:2:1.
Seforno: Although Yaakov heard about what Reuven did, he did not exclude him from the count of sons, since he was convinced that he had done Teshuvah immediately. 2
Hadar Zekenim citing Ibn Ezra: When Yaakov heard that Reuven slept with Bilhah, 3 he separated from his wives and did not father more children.
Rosh: Because Yaakov already fathered all the children he was destined to, Reuven pretended to sleep with Bilhah, so Yaakov would not lie with her, due to shame. "Va'Yishma Yisrael" - when he found out that he did not sin, and his good intent, Bnei Yaakov were 12, i.e. all Tzadikim.
Moshav Zekenim #1: It teaches that there was no need for Reuven to sin with Bilhah to forbid her to Yaakov, for Yaakov was not going to father any more sons.
Moshav Zekenim #2: Until now there were 13 portions for inheritance. Now Reuven lost his Bechorah, so there were only 12.
Ramban: Although Yaakov heard about what Reuven did, due to his humility, he did not exclude him from his household or say that he will not inherit with his brothers.
Malbim, from the Ari Zal: Yaakov had been destined to father Efrayim and Menasheh that night. Hashem blessed him "Perei u'Rvei" (35:11), i.e. two more sons in addition to Binyamin, who had already been conceived. Yaakov wanted that they should be from Bilhah, so they would be considered Rachel's; Reuven knew the 'destiny,' and wanted that they be from his mother, therefore he disturbed Yaakov's bed. Due to Reuven, Yaakov did not father them; he had only 12 sons. This is why he decreed that Efrayim and Menasheh will be considered like his sons (48:5). 4
And that he is still therefore included in the 12 tribes (Rashi, Devarim 33:27). In fact, this was Hashem's direct answer to Yaakov who was afraid that a wicked son had emerged from him, just as Yishmael had emerged from Avraham and Esav from Yitzchak (Targum Yonasan).
As the Gemara says in Berachos 19a, 'If you see a Talmid-Chacham perform a sin at night, do not think evil of him by day, because he is sure to have done Teshuvah.' (EC)
Hadar Zekenim, citing a Midrash: Reuven put egg white (which resembles semen) on Bilhah's bed. When Yaakov saw it, he suspected that he slept with her, and excluded him from the Shevatim. Va'Yishma Yisrael - he tested and saw that it is not semen.
Malbim: Reuven's Bechorah was given to Yosef (Divrei ha'Yamim I 5:1). This was not a punishment. Rather, it was to fulfill Hashem's word, "Perei u'Rvei," and to consider Efrayim and Menasheh like Yaakov's sons, without causing a loss to the other brothers. Reuven's Mazal understood that his sin will be fixed through sons that will come from Yosef. Therefore, when he saw that Yosef is not in the pit, he said "va'Ani, Anah Ani Va" (37:30; i.e. how will I fix my sin?!)
Why is there a Pesik (Parshah break) in the middle of the Pasuk?
Ramban: To teach us that, 'although there begins a new topic, the listing of the tribes, Reuven did not lose his place among them on account of what he did.'
Rashbam: The second half of the Pasuk really belongs immediately after the birth of Binyamin (in 35:18), at which point Yaakov had 12 sons; 1 only the Torah waited until it had finished with the Parshah concerning Rachel's death, and inserted it here.
QUESTIONS ON RASHI
Rashi writes that Reuven switched Yaakov's bed. Why did he do that?
Rashi: In honor of his mother, as he considered it a slight to her to place Rachel's maidservant on a par with her.
Ramban: In order to prevent Yaakov from bearing any more children. He was afraid that an additional son would take a portion of his father's inheritance, causing him, as the Bechor (who was destined to inherit a double portion), to lose more than his brothers. 1
Malbim: Refer to 35:22:6:9.
His mother Leah, did not worry him, since she was already old, and as for Zilpah, either she was no longer alive, or he would not dare move her bed, since she was her mother's maidservant. This also explains why Yaakov punished Reuven by taking the Bechorah away from him ('Midah k'Neged Midah'). And it also explains why the Pasuk ends "and the sons of Yaakov were 12 - inasmuch as he did indeed have no more children (Ramban).
Rashi writes: "... The verse considers it as if he had lain with her." How can we interpret the verse in its simple sense?
Maharal (Chidushei Agados Vol. 1, p. 33, to Shabbos 55b): On Yaakov's level, intimacy is expressed as Chibur (connection). 1 Reuven's deed prevented Yaakov's connection (with Bilhah - refer to 35:22:3.1:1), and was therefore tantamount to laying with her. 2