While Israel dwelt in that land Rueben went and lay with Bilhah his father’s concubine; and Israel heard of it. Gen. 35:22
There is never a reason given for his act. Rueben was the first born of Jacob. His mother was Jacob’s first wife Leah. Bilhah had been Rachel’s hand maid, and in a reproductive war of one-up-man-ship with her sister Leah, Rachel had given Bilhah to Jacob as a wife. (See Also: Three Kinds of Wives)
Many reasons for his act have been suggested.
The most predominant reason given is that of being a total pervert. This seems unlikely however as many others at the time were stuck down for bad behavior of one kind or another. Yet God himself says nothing about this.
Then there is the one that says his actions represent some kind of vengeance for his mother. It is suggested that after Rachel’s death Jacob may have gone on and on mourning, and his first wife instigated this wickedness, to show Jacob that nothing which came from Rachel was true or faithful. This view relies heavily on the similarity of the tale with the Greek myth of Amyntor and Pheonix, where Pheonix at the instigation of his mother slept with his father’s mistress.
The least of the suggestions comes from the liberal neo-orthodox theologians who deny that the first five books of Moses are a literal historical narratives. They believe that the Torah was not written by Moses at all and instead that it was the writings of 4-5 people at the time of Ezra who are trying to give the Jews a national identity. Further they wrote a history based on old traditions, legends, and myths that many of the people held. According to them this was a symbolic passage about the tribe of Rueben lording over the tribes of Dan and Naphtali, who were Bilhah sons. Aside from the absolute absurdity of this opinion, there is no historical evidence that the tribes of Rueben ever did anything for the tribes of Dan or Naphtali. The tribes of Dan and Naphtali were in the north, in what is now southern Lebanon, and the tribe of Rueben was east of the Jordan in what is now Jordan. No judge, prophet, nor prince, ever came from that tribe, nor any persons of renown except Dathan and Abiram, who had rebelled against Moses [Num 16].
Truth is we are not told what Rueben’s reasons were. However the one that makes the most sense considering the historical cultural background, is that Rueben was trying to become the head of the clan before Jacob’s death. Just as Absalom did when he usurped David’s throne.
Ahithophel said to Absalom, “Go in to your father’s concubines, whom he has left to keep the house; and all Israel will hear that you have made yourself odious to your father, and the hands of all who are with you will be strengthened.” So they pitched a tent for Absalom upon the roof; and Absalom went in to his father’s concubines in the sight of all Israel. 2 Sam. 16:21-22
Then there is Solomon who may of done the same. He may have taken David’s last wife, Abishag the Shunammite. This belief relies one the assumption that Shunammite and Shulammite are the same place and that one is a spelling error. This makes Abishag the object of Solomon’s affections in The of Songs of Solomon.
1 Now King David was old and advanced in years; and although they covered him with clothes, he could not get warm. 2 Therefore his servants said to him, “Let a young maiden be sought for my lord the king, and let her wait upon the king, and be his nurse; let her lie in your bosom, that my lord the king may be warm.” 3 So they sought for a beautiful maiden throughout all the territory of Israel, and found Abishag the Shunammite, and brought her to the king. 4 The maiden was very beautiful; and she became the king’s nurse and ministered to him; but the king knew her not. 1 Kings 1:1-4
He was Jacob’s firstborn. He was the son of his first wife. Yet for all this right of position Ruben is not given the leadership of the tribes. His descendants are not the line of kings. That honor will go to Judah, (even though Judah had children by his daughter-in-law, Tamar).
Forty years after this event, when Jacob was blessing to his sons, says of Rueben.
3 Reuben, you are my first-born, my might, and the first fruits of my strength, pre-eminent in pride and pre-eminent in power. 4 Unstable as water, you shall not have pre-eminence because you went up to your father’s bed; then you defiled it — you went up to my couch! Gen. 49:3-4
In the Hebrew it is reckless as water, and water is reckless if it is not contained. Water goes where ever it wills, and always takes the path of least resistance. Historically the tribe of Rueben stayed on the east of the Jordan because it was already conquered and good for grazing. It was the easy way.
The man Rueben may have thought that he had gotten away with his sin. Yet for all his generations, his tribe lost the power and position that should have been theirs, because of the sin of the ancestor.
. . . visiting the iniquity of the fathers upon the children to the third and the fourth generation of those who hate me, Ex. 10:5b
He who commits adultery has no sense; he who does it destroys himself. Wounds and dishonor will he get, and his disgrace will not be wiped away. Prov. 6:32-33
The only way to break one of these generational curses, is to repent, denounce the sinners that have come before and walk with God.
. . . withholds his hand from iniquity, takes no interest or increase, observes my ordinances, and walks in my statutes; he shall not die for his father’s iniquity; he shall surely live. Ezek. 18:17