Ramban on Genesis 34:1/רמב"ן על בראשית ל״ד:א׳

1THE DAUGHTER OF LEAH, WHOM SHE HAD BORNE UNTO JACOB. The reason [Scripture specifies the daughter of Leah] is to state that she was the sister of Simeon and Levi, who were envious for her sake and avenged her cause. And Scripture mentions further, whom she had borne unto Jacob, in order to allude to the fact that all the brothers were envious for her.