Reference for Pesachim 76:7

ותיפוק ליה דהוה ליה מצה עשירה

It was taught in accordance with Rabbah: You might think that he can discharge his obligation with the loaves of the thanksoffering and the wafers of a nazirite, therefore it is stated, 'And ye shall guard the unleavened bread', teaching [that it must be] unleavened bread which is guarded for the sake of [fulfilling the obligation of eating] unleavened bread, thus excluding this which is guarded not for the sake of unleavened bread but for the sake of a sacrifice.

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