שמות, פרק י״ב, פסוק י״ח

The transition from slavery to freedom is anchored in a precise and clearly defined timeframe. The laws surrounding the eating of matzah and the prohibition of leavened bread create strict boundaries of days and nights. This framework distinguishes between absolute obligations and optional practices, while also establishing the foundational structure of the Jewish calendar. The timing begins in the first month of the year, known as Nissan [אבן עזרא, רלב״ג, ביאור יש״ר, שטיינזלץ]. The start of the holiday on the evening of the fourteenth day refers to the night that follows the fourteenth [שטיינזלץ]. Referencing this specific day also serves as a reminder of the preliminary requirement to clear out all leavened bread during the daylight hours of the fourteenth, before the holiday officially commences [תורה תמימה].

The primary approach among commentators is that these instructions combine two distinct levels of practice. Consuming matzah on the very first night is an absolute obligation [העמק דבר, רלב״ג, גור אריה, רש ר הירש]. This specific duty is binding for all generations, even today when the Passover sacrifice is no longer offered [תורה תמימה, פרדס יוסף, רש ר הירש]. In contrast, for the remainder of the holiday—continuing until the evening of the twenty-first day—eating matzah becomes optional. God does not demand continuous consumption of matzah for seven days, as that would be neither possible nor reasonable. Instead, the requirement for the rest of the week is simply an absolute ban on eating leavened bread [רלב״ג, העמק דבר]. Nevertheless, those who choose to continue eating matzah on the subsequent nights still fulfill a divine command and receive a reward for doing so [ריב״א].

Since other instructions already state that the holiday lasts for seven days, detailing the exact end date might seem redundant. However, commentators agree that this addition specifically addresses the nights. While the term "days" could be misunderstood as applying only to daylight hours, the precise dates emphasize that the prohibition against owning and eating leaven applies equally to all the nights within that week [רש״י, מזרחי, שפתי חכמים, גור אריה, יריעות שלמה]. Furthermore, defining the exact dates ensures that the seven days are observed consecutively, rather than intermittently or postponed to the end of the month [חזקוני, פענח רזא]. This precise wording also prevents a miscalculation where one might start counting the seven days only on the evening following the fifteenth, which would mistakenly extend the holiday until the twenty-second day [פענח רזא].

Setting the boundaries from one evening to the next serves as a fundamental source for the Jewish calendar, establishing that a full day begins at nightfall [תורה תמימה, רלב״ג, פרדס יוסף]. On a conceptual level, eating matzah on that first night represents the departure from human bondage and the entry into the service of God. The social freedom granted by God is deeply intertwined with devotion to Him, ensuring that the liberated Israelites continually stand before God holding the symbol of their freedom [רש ר הירש]. To mark the definitive conclusion of this sacred period, a custom developed based on ancient traditions to taste leavened bread immediately after the evening of the twenty-first day. This act creates a clear and tangible distinction between the time of restriction and the return to everyday life [תורה תמימה, פרדס יוסף].