Midrasch zu Bereschit 34:26

For in their anger they slew a man (Gen. 49:6). Did they slay only one man? Is it not written: And they came upon the city unawares, and they slew all the males (ibid. 34:25)? The fact is that they were all considered by the Holy One, blessed be He, and by them as one man, as Scripture states: And thou shalt smite the Midianites as one man (Judg. 6:16). Similarly, it states: The horse and its rider hath He thrown into the sea (Exod. 15:1).

And they took Dina (Gen. 34:26), Rabbi Yudan said: they dragged her and went out. Rav Huna: a woman who was penetrated by an uncircumcised man is difficult to separate. Said Rav Huna: she kept saying 'and I, where will I go with my shame?' until Shime'on swore to her that he would take her [as wife], since it is written "and Sha'ul the son of the Canaanite woman" (Genesis 46:10) - he was the son of Dinah, who was penetrated by a Canaanite. Rabi Yehudah and Rabi Nechemiah and the rabbis: Rabi Yehudah said that she did the act of a Canaanite. Rabbi Nechemiah said that she was penetrated by a Chivi that is considered a Canaanite. And the rabbis say: Shime'on took her as a wife and she died in the land of Canaan.