Genesis 35:22

And he lay. In the midst that he disturbed his bed, Scripture accounts it to him as if he had sexual relations with her. And why did he disturb his bed? That when Rachel died, Jacob removed his bed that had been regularly in the tent of Rachel and not in the other tents and he placed in the tent of Bilhah. Reuben came and saw this as an insult to his mother. He said, " If my mother's sister was my mother's rival, why then would the handmaid of my mother's sister, become my mother's rival? For this, he disturbed (the bed).

And it was while Israel dwelt in this land that Reuben went and confounded the bed of Bilhah the concubine of his father, which had been ordained along with the bed of Leah his mother; and this is reputed with regard to him, as if he had lain with her. And Israel heard it, and it afflicted him, and he said, Alas, that one should have come forth from me so profane, even as Ishmael came forth from Abraham, and Esau from my father! The Spirit of Holiness answered and thus spake to him: fear not, for all are righteous and none of them is profane! So, after Benjamin was born, the sons of Jakob were twelve.

AND ISRAEL HEARD OF IT. Scripture relates Jacob’s humility. He heard that his son had profaned his couch, but yet he did not command them to remove him from his house and from inclusion among his sons so that he should not inherit with them. Instead, he is counted among them, as it is written, And the sons of Jacob, were twelve, and he is counted first. It is for this reason that Scripture has combined the two sections of the Torah. Then a new section begins, And the sons of Jacob were twelve. Ramban explains why the Masorah combines them into one verse. through one verse. For although this is the beginning of a subject wherein Scripture commences to count the tribes now that they were all born, it hints that Reuben was not rejected on account of his deed.
In line with the simple meaning of Scripture it is possible that Reuben disturbed the couch of Bilhah [Rachel’s handmaid] because he feared that she might give birth again from Jacob, for he, being the first-born and thinking of taking two portions of the inheritance, would thus lose more than all the brothers. He had no fear of his mother for she was elderly. Zilpah had perhaps died, or it may be that he had concern for his mother’s honor, and since Zilpah was her handmaid, he did not disturb her. It was for this reason that the right of the first-born was taken away from Reuben, measure for measure. And this is the purport of the verse, And the sons of Jacob were twelve, meaning that he did not beget children after that.

וישמע ישראל, this matter has been reported only so that we can understand why Yaakov passed over his firstborn son Reuven when in his blessings before his death he referred to him as פחז כמים אל תותר כי עלית על משכבי אביך (49,4). “the one who was as unrestrained as water when you mounted the bed of your father, does not deserve the privileges associated with the birthright.” [These privileges were allocated by Yaakov in part to Yehudah, commencing with the reign of David, and in part to Joseph, as the firstborn son of Rachel. The latter was accorded two tribal heads, (Ephrayim and Menashe) among the twelve tribes. Ed.]

וישמע ישראל..ויהיו בני יעקב שנים עשר. Even though Yisrael had heard about this major indiscretion by his firstborn son Reuven, he did not exclude him from the number of children he called “my sons.” This was because he was convinced that Reuven had immediately repented his mistake. His indiscretion therefore did not leave a permanent stain on the future development of the Jewish people and the status of all the tribes surviving any future catastrophes [such as when the wars prior to the arrival of the Messiah would be fought. Ed.]

ויהי בשכון, Yaakov did not reside anywhere until he came to his father; however, seeing that he had so many animals and possessions that he moved extremely slowly, it appeared as if he was actually settling down.

וילך ראובן, he went to Bilhah’s tent and slept with her.

פלגש אביו, his father’s concubine. Actually, she was his father’s wife, but in Reuven’s view she was no better than a concubine. Reuven did not consider her as out of bounds to him as she had been a slave woman originally, and his father had subsequently taken her to be his concubine. The Torah clearly states that she had become Yaakov’s proper wife in all matters legal. (30,4) As such Bilhah was totally out of bounds to him. Even before the giving of the Torah, the laws of incest governing all of mankind (Noachide laws) included the prohibition of sleeping with one’s father’s wife. (compare our commentary on 20,24) If such legislation applied to all of mankind, how much more so did it apply to the sons of Yaakov. As a result of this trespass Reuven’s status as Yaakov’s legal firstborn was revoked on Yaakov’s deathbed when he publicly announced his unfitness for the title as we also know from Chronicles I 5,1, and his position was given to Joseph instead.

וישמע ישראל, he stopped living with Bilhah as a result of this. The meaning of the line ויהיו בני יעקב שנים עשר, is that from that time on Yisrael had no further children. He no longer slept with any woman for the remainder of his life. In fact, he basically became a recluse, not attending to mundane activities but concentrating on serving G’d directly. This is what he had meant when he said in his vow, that once he would return safely to his father’s house, והיה ה' לי לאלוקים, “the Lord will be my G’d.” According to the Talmud Shabbat 55 Reuven had not actually slept with Bilhah at all, but had only made her bed look slept in, disturbed, to give the impression that intimacy had taken place there. This was a protest against his father not only having spent most of his married life with Rachel, but even now after her death spending his time with Rachel’s maidservant instead of with his mother, with Leah.

וישכב את בלהה פלגש אביו, “he lay with Bilhah, the concubine of his father.” According to some commentators (Talmud tractate Shabbat folio 55,) all he did was that he removed her couch from his father’s tent. This occurred before Yaakov had returned to his father’s house. The Torah treats the deed as if Reuben had committed incest with his aunt. Our author points to Job 31,12, [he could have used the entire sequence from verse 1 to there Ed.] as proof that harbouring incestuous thoughts may be considered as if one had carried out what one had fantasized about. Ed.