Midrash su Genesi 31:50

Another interpretation (of Gen. 37:35): BUT HE REFUSED TO BE COMFORTED. It is simply that our father Jacob said: See, the tribal covenant has been broken! How I have toiled to raise up twelve tribes. Now I see that, since Joseph has gone, behold the very covenant has ceased. All the works of the Holy One correspond to twelve tribes: twelve constellations, twelve months, twelve hours in the day, twelve hours in the night, twelve stones which Aaron wore < on his breastplate >. But now Joseph has gone! Behold, the tribal covenant has been broken. But did Jacob not know how to take a wife and sire a son so that there would be twelve tribes? < He did not do so > simply because he had kept a vow to Laban, as stated (in Gen. 31:50): IF YOU MISTREAT MY DAUGHTERS OR TAKE WIVES BESIDES MY DAUGHTERS, even after their death < …. > What did Laban do? He brought him outside. He said to him (ibid., cont.): THOUGH NO ONE IS WITH US, SEE, GOD IS A WITNESS…. Because of that vow, he was unable to take a wife. When his sons saw that he was complaining so and that he would not accept consolation, they went to Judah and said to him: You have made all this great misfortune for us! He said to them: I said to you (in Gen. 37:26): WHAT PROFIT < IS THERE IF WE KILL OUR BROTHER AND CONCEAL HIS BLOOD >? Now are you saying: What have you done? They said to him: But did we not hearken to you < when > you said (Gen. 37:27): COME, AND LET US SELL HIM TO THE ISHMAELITES? So we hearkened to you. If you had said: Come, and let us return him to his father, should we not have hearkened to you? In that hour, therefore, they arose and expelled him. How is it shown? From what they read on the matter (in Gen. 38:1): JUDAH WENT AWAY.

Why did Jethro compel him to take an oath? Lest he do to him what Laban had stated: If thou shalt afflict my daughters and take wives (Gen. 31:50). The Holy One, blessed be He, said to him: The righteous Moses risked his life for the sake of My children and was forced to flee to Midian, but he will redeem them from Egypt. Therefore it is written: And Moses was keeping the flock (Exod. 3:1).