Or HaChaim on Shemos 1:1

English: ואלה שמות בני ישראל , And these are the names of the children of Israel, etc. The reason that the Book of Exodus commences with the conjunctive letter ו is to teach that all these people were righteous, just like their parents. The word ואלה also is employed to show continuity with the people who had preceded them. In this instance the preceding people were Abraham, Isaac and Jacob, all of whom were outstandingly righteous. The generation mentioned at the opening of the Book of Exodus too were righteous people. Another reason for the letter ו in this instance is to remind us that the years of exile of the Jewish people were computed as having already begun during the time of Abraham, not merely after the arrival of Jacob in Egypt (compare Tanchuma Shemot 4). Still another reason for the Torah writing that letter is to tell us that just as the earlier generations perceived that they were in exile and accepted their fate without resentment, so the generation of which we read here also accepted their destiny without complaint. Perhaps this will help us understand why the Torah bothered to list the names of the tribes when we have been well aware of their names since the Book of Genesi