Reference for Bekhorot 4:59

דעיקר מכירה היא

Likewise here also when [the Mishnah] lays down that selling [is prohibited] the same ruling applies to kablanuth.<span class="x" onmousemove="('comment',' Where the heathen undertakes to take care of the Israelite's animal in return for its offspring.');">³⁶</span>

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