The Allusion to the Second Day Yom Tov in Galus

שמות פרק יג , ז מַצוֹת יֵאָּכֵל אֵת שִבְעַת הַיָּּ מִים

The word את (which connotes an addition) is unclear in this verse. Some say this alludes to the concept of the second day Yom Tov in Galus. Thus, Pesach is eight days long (an addition to the standard 7 days). This allusion has a further basis since the numerical value of את is 401, the same as the word שמונה. And just like by the burning bush where Moshe did not want to inform the Jews of additional exiles (as brought by Rashi), so here the Torah did not state this concept directly of an extra day, which would hint at Galus.