Reference for Bava Batra 322:2

ודלמא בשמיה דאבוה חתם לא שביק איניש שמיה דידיה וחתים בשמיה דאבוה

For, surely, Rab drew a fish;<span class="x" onmousemove="('comment',' Instead of his and his father's full name. This symbol has this become his recognised and legally valid signature. ');">⁵</span> R. Hanina drew a palm-branch;<span class="x" onmousemove="('comment',' Instead of his and his father's full name. This symbol has this become his recognised and legally valid signature. ');">⁵</span> R. Hisda a Samek.<span class="x" onmousemove="('comment',' One letter of his name. ');">⁶</span> R. Hoshaia, an Ayin,<span class="x" onmousemove="('comment',' One letter of his name. ');">⁶</span>

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