Seven Days of Matzah and the Festival Offering

Mekhilta DeRabbi Shimon Ben Yochai 13:5

"Seven days you shall eat unleavened bread" (Exodus 13:6). How do you know that if the six days of the festival pass and one did not bring the festival-offering, he is still obligated in the festival-offering for all seven? Scripture says, "Seven days you shall eat unleavened bread, and on the seventh day there shall be a festival to the LORD."

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