Reference for Chullin 161:20

כל הראוי לבא לאחר זמן הרי הוא בלא תעשה ואין בו כרת

Now upon this was raised the following difficulty: [You say,] Where both were consecrated animals and they were slaughtered outside, [he who slaughtered] the second has transgressed a negative command [and nothing more]?

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