"from the first day until the seventh day": Its punishment is for seven days; the exhortation against it obtains always. For it would follow (otherwise), viz.: Since (eating chametz is punishable by kareth, and (eating) forbidden fats is punishable by kareth, then if we have learned about forbidden fats that its punishment is equivalent (in time) to its exhortation, then the same applies to chametz. It is, therefore, written "from the first day until the seventh day"—Its punishment is seven days, but its exhortation obtains always. We have heard its punishment, but we have not heard its exhortation. It is, therefore, written (Devarim 16:3) "Do not eat chametz upon it."