Reference for Makkot 44:4

אין אומדין אלא במכות הראויות וכו': לקה אין לא לקה לא

We only evaluate for malkus that are fit to. etc.: If he was already flogged then yes, [a differing evaluation would exonerate him. This implies that] if he wasn't already flogged then [a differing evaluation] would not [exonerate him.].

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