Commentary for Exodus 13:7

מצות יאכל את שבעת הימים,“unleavened bread shall be eaten during the duration of these seven days.” The expression את שבעת הימים is the same as if the Torah had written בשבעת הימים “on these seven days.” We find something similar in Chronicles II 30,22 ויאכלו את זבחי המועד שבעת ימים, “they ate of the sacrifices of the festival during the seven days.” Our sages there mention that the word את is meant to include the last eight hours of the 14th of the month, or if they were outside the boundaries of Eretz Yisrael that they observed an eight’s day of Passover. [Rabbi Chavell, basing himself on Torat Chayim, claims that the fact that apparently matzah was permitted already two hours before noon on the fourteenth of Nissan is proof that chametz was already forbidden. Ed.]