Reference for Bava Kamma 70:16

והא לא דמיא רישא לסיפא

and the defendant certain. And if the concluding clause deals with a case where the plaintiff was doubtful and the defendant certain, we should suppose that the opening clause<span class="x" onmousemove="('comment',' Where the defendant pleads that 'the pursued ox was injured by a rock…'. ');">¹³</span>

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