Reference for Gittin 173:8

א"ל רבינא לרב אשי ומאי שנא מהא דתניא הכותב כל נכסיו לשני עבדיו קנו ומשחררין זה את זה

— Mar Kashisha the son of R. Hisda said to R. Ashi: We state as follows in the name of R. Johanan, that [this rule applies] where it is written with each one, On the first day of the week, on the first day of the week.<span class="x" onmousemove="('comment',' I.e., they are all written and signed on the same day. ');">⁸</span>

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