Reference for Bava Batra 327:5

דכתבי הכי אנחנא סהדי חתמנא על מחקא ושטרא כתב על ניירא

An objection was raised: [A deed] the text<span class="x" onmousemove="('comment',' Lit., 'it'. ');">¹³</span> [of which is written] on [clean] paper<span class="x" onmousemove="('comment',' I.e., on which nothing has ever before been written. ');">¹⁴</span> and its witnesses on an erasure is valid. Is [there no cause] to apprehend that [the text] might be erased, and any [terms] one desires substituted,<span class="x" onmousemove="('comment',' Lit., 'write'. ');">¹⁵</span>

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