Why Judah Went Down and the Twin Sisters of the Tribes

[(Genesis 38:1:) "And Judah went down [from his brothers, and turned aside to a certain Adullamite]."] This is what the verse says (Micah 1:15): "I will yet bring to you one who shall dispossess you, [O inhabitant of Mareshah; to Adullam shall come the glory of Israel]." R. Judah and R. Nehemiah [differed]. One said: The tribes married their sisters, as it is said (Genesis 37:35): "And all his sons and all his daughters arose to comfort him." And how many daughters were there? Rather, they were their twin sisters, for [the mother] would bear twins together with [each son], and he would take her [as a wife]. And thus it says regarding Benjamin (Genesis 35:17): "for this too is a son for you." "For this is a son for you" is not stated, but rather "for this too" — that his mother bore a twin sister along with him. Hence (ibid. 37:35): "And all his sons and all his daughters [arose]." From here you learn that they married their sisters. And R. Nehemiah upholds [the verse by interpreting] "his daughters" as his daughters-in-law, for a man's son-in-law is like his son and his daughter-in-law like his daughter, and a man does not refrain from calling his daughter-in-law his daughter. Our Rabbis said: Judah, who was the eldest in his father's house, took a Canaanite woman, as it is written (Genesis 38:2): "And Judah saw there [the daughter of a certain Canaanite]." And the prophet proclaims (Micah 1:15): "To Adullam shall come the (Holy One) [glory] of Israel." Hence (Genesis 38:1): "And Judah went down [from his brothers] and turned aside to a certain Adullamite."