Reference for Bava Batra 150:16

לימא כהני תנאי דתניא ספינה נקנית במשיכה ר' נתן אומר ספינה ואותיות נקנות במשיכה

for, since one foreleg and one hind leg have been moved, the other legs are on the point of being moved<span class="x" onmousemove="('comment',' And, in law, are regarded as having already moved. ');">³⁸</span> but [in the case of a ship] if he pulls it all, he does [acquire possession]; otherwise, [he does] not.<span class="x" onmousemove="('comment',' Because the shifting of part of a ship does not lift the whole ship completely out of its place. ');">³⁹</span> Must it be said that [they<span class="x" onmousemove="('comment',' Rab and Samuel. ');">⁴⁰</span> differ on the same principles] as the following Tannaim? For it has been taught: A ship is legally acquired by <i>meshikah</i>. R. Nathan said: A ship and letters<span class="x" onmousemove="('comment',' I.e., a bond, note of indebtedness. ');">⁴¹</span> are legally acquired by <i>meshikah</i><span class="x" onmousemove="('comment',' The buyer of the bond acquires legal right to the debt recorded thereon by the meshikah of the bond. ');">⁴²</span>

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