Reference for Zevachim 212:15

תיתי בק"ו ממותיר מה מותיר שלא ענש הזהיר פסח ומילה שענש אינו דין שהזהיר

[Nor can you deduce it] from all these because they are never permitted exceptionally. Raba said: If I have a difficulty, it is this: When we learnt, The Passover-offering and circumcision are positive commands,<span class="x" onmousemove="('comment',' It is stated in Ker. ');">¹⁹</span>

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