The Torah prohibits chametz in two locations during Passover: in your houses and in your boundaries. But a careful reader might wonder whether these two prohibitions share the same time limit. Perhaps chametz is banned from your house for seven days but from your broader territory — your boundaries, your land — forever?
The Mekhilta anticipated this reading and shut it down with a precise textual argument. (Exodus 13:7) states, "and leaven shall not be seen in all of your boundaries for seven days." The phrase "for seven days" is attached directly to "boundaries." Just as the prohibition in your houses lasts seven days, so the prohibition in your boundaries lasts seven days. The two are parallel. Neither extends beyond the festival.
This might seem like an obvious point, but the rabbis never assumed anything was obvious in the Torah. Every word, every phrase, every apparent redundancy demanded explanation. If the Torah mentions both "houses" and "boundaries," perhaps it intends different rules for each. The Mekhilta's response is that the identical time qualifier — seven days — governs both domains equally.
The practical consequence is clear: once Passover ends on the evening following the seventh day, chametz is immediately permitted again in both your home and your wider territory. The prohibition is intense but bounded. It fills seven days completely, then releases its hold entirely.