Chapter 41(Yes, this is out of sequence; the story of Judah and Tamar takes place later in the Book of Jubilees than in Genesis.) Gen. 38 states that Er, Judah's eldest son, was killed by God because he was "wicked in the sight of the Lord". Jubilees concurs but adds beforehand:
But he hated her, and did not lie with her, because his mother was of the daughters of Canaan, and he wished to take him a wife of the kinsfolk of his mother, but Judah, his father, would not permit him.
In the Bible, after Er and Onan have died, Judah will not allow his third son Shelah to marry the unfortunate Tamar. Jubilees, seeking to preserve the reputation of Judah, shifts this blame onto his wife, the daughter of Shua`, unnnamed in the Bible but here named as Bedsu'el.
The Biblical version of the story ends with, "Judah said, 'She has been more righteous than me, because did not give her to Shelah my son.' And he knew her again no more." Jubilees fleshes this out more:
Judah acknowledged that the deed which he had done was evil, for he had lain with his daughter-in-law. He esteemed it hateful, and acknowledged that he had transgressed and gone astray in uncovering the skirt of his son, and he began to lament and to supplicate before the Lord because of his transgression. So we told him in a dream that it was forgiven him because he supplicated earnestly, and lamented, and did not again commit it; and he received forgiveness because he turned from his sin and from his ignorance, for he transgressed greatly before our God.The narratorial angel then uses this as the opportunity to lay down to Moses the law, to teach the Israelites, concerning punishment for those who sleep with their mothers- and daughters-in-law; concluding:
We told Judah that his two sons had not lain with her, and for this reason his offspring was established for a second generation, and would not be rooted out. For in singleness of eye [meaning in ignorance, apparently], Judah had sought to punish her by burning with fire, according to the judgment with which Abraham had commanded his sons.
Chapters 35–38Back where we were (chapter 35), there now follows a three-chapter story which is not in the Bible at all, about Isaac's death. The Bible told this non-chronologically, at an earlier point, to wrap up the story of Isaac; I'm going to defer it until next week because this week's post is long enough already, and there's otherwise only one paragraph to next week's post.
In the narrative of the attempted seduction of Joseph by Potiphar's wife, she locks the door and Joseph has to break through it to get out. Presumably this is intended to depict an ancient origin for the prohibition on יִחוּד, a man and woman who are not married to each other being left alone in the same space. (I have no doubts that such a custom did actually go back to the Patriarchal age.)