Pesachim 66A

אמר לו רבי עקיבא, או חלוף: מה אם הזאה שהיא משום שבות ⁠— אינה דוחה את השבת, שחיטה שהיא משום מלאכה ⁠— אינו דין שלא תדחה את השבת?! אמר לו רבי אליעזר: עקיבא, עקרת מה שכתוב בתורה: ״במועדו״, בין בחול בין בשבת.

R' Akiva said to R' Eliezer: Or perhaps we can reverse the order of your argument and say the opposite: If, as we know by accepted tradition, sprinkling the purifying water on Shabbat, which is prohibited only due to rabbinic decree, does not override Shabbat, then with regard to slaughter, which is prohibited as a biblically prohibited labor, is it not right that it should not override Shabbat? Therefore, it should be prohibited to slaughter the Paschal lamb when the eve of Passover occurs on Shabbat. R' Eliezer said to him: Akiva, how can you say this? You have thus uprooted what is written in the Torah: “Let the children of Israel offer the Paschal lamb in its appointed time” (Numbers 9:2); the phrase “at its appointed time” indicates that the offering must be brought on that day, whether it is a weekday or Shabbat.

אמר לו: רבי, הבא לי מועד לאלו, כמועד לשחיטה. כלל אמר רבי עקיבא: כל מלאכה שאפשר לעשותה מערב שבת ⁠— אינה דוחה את השבת. שחיטה, שאי אפשר לעשותה מערב שבת ⁠— דוחה את השבת.

R' Akiva said to R' Eliezer: my teacher! bring me an appointed time stated in the Torah for these tasks, namely, carrying the animal or bringing it from outside the Shabbat limits, like the appointed time stated with respect to slaughter. The Paschal lamb must be slaughtered on the 14th of Nisan, but there is no fixed time when the animal must be brought to the Temple, and it is therefore possible to transport it before Shabbat. R' Akiva stated a principle: Any prohibited labor required for the offering of the sacrifice that can be performed on Friday does not override Shabbat; slaughter, which cannot be performed on Friday, overrides Shabbat.