Pesachim 96B

אלא אחמץ. מכלל דפסח מצרים לילה אחד ותו לא? והתניא, רבי יוסי הגלילי אומר: מנין לפסח מצרים שאין חימוצו נוהג אלא יום אחד ⁠— תלמוד לומר: ״לא יאכל חמץ״, וסמיך ליה: ״היום אתם יוצאים״.

Rather, it refers to leavened bread, which is prohibited all 7 days of Passover in the generations following the Exodus. The Talmud asks: Does this prove by inference that during the Passover of Egypt, leaven was prohibited for only one night and not more? But wasn’t it taught in a baraita that R' Yosei HaGelili says: From where is it derived with regard to the Passover of Egypt that its prohibition of leavened bread applied for only one day? The verse states: “No leavened bread should be eaten” (Exodus 13:3), and juxtaposed to it the verse states: “This day you go forth” (Exodus 13:4), to teach that the prohibition of leaven applied in Egypt for only one day. In any event, the prohibition applied for an entire night and day, and not just one night.

אלא הכי קאמר: לילה אחד, והוא הדין לפסח דורות. וחימוצו כל היום, ופסח דורות נוהג כל שבעה.

Rather, this question must be answered by saying that this is what it said in the Mishnah: The Paschal lamb was eaten in Egypt on one night, and the same is true of the Paschal lamb of later generations; and its prohibition against leavened bread applied the entire day, and on Passover in later generations it applies to all 7 days of the Festival.

מתני׳ אמר רבי יהושע: שמעתי שתמורת פסח קריבה, ותמורת פסח אינה קריבה, ואין לי לפרש.

Mishnah: R' Yehoshua said: I heard two rulings from my teachers: One ruling was that the substitute of a Paschal lamb is sacrificed as a peace-offering after Passover, and another ruling was that the substitute of a Paschal lamb is not sacrificed as a peace-offering after Passover; and I cannot explain these two rulings, as I do not remember the circumstances to which each ruling applies.