Reference for Makkot 44:5

ורמינהו אמדוהו לקבל ארבעים וחזרו ואמדו שאין יכול לקבל ארבעים פטור אמדוהו לקבל שמונה עשרה וחזרו ואמדוהו שיכול לקבל ארבעים פטור

But I'll challenge that [with the following baraisa:] If they evaluated him to be able to withstand forty and then reevaluated him to be unable to withstand forty, he is exonerated. If they evaluated him to be [only] able to withstand eighteen and then reevaluated him to be able to withstand [the full] forty, he is exonerated. [Thus implying that he gets exonerated even if he wasn't yet flogged at all!]

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