Reference for Bava Metzia 145:9

אמר להו שמואל להנהו דשבשי שבשא הפוכו בארעא כי היכי דקני לכו גופא דארעא ואי לא הויא לכו כהלואה ואסור

it does not look like payment for waiting.<span class="x" onmousemove="('comment',' But as a speculation. He may (and probably will) receive more than his money's worth, but on the other hand he may lose it. ');">¹⁶</span> R. Shimi b. Hiyya said: But Rab agrees [where the ploughing is done] with [the aid of] oxen, since great loss is caused.<span class="x" onmousemove="('comment',' V. supra 30a top. Hence there is a greater element of risk which converts it into a speculation. [Tosaf.: Cattle breeders (who buy the offspring before it is born) since the risks are great.] ');">¹⁷</span>

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