Reference for Chullin 229:5

השתא ומה שבת דחמירא מעשיה מותרים הני לא כל שכן

Furthermore if a man ploughed with an ox and an ass together, or if he muzzled a cow when it was treading out [the corn], should it<span class="x" onmousemove="('comment',' I.e., the produce of the field which had been so ploughed and the corn which had been so trodden (Rashi) ; or, the ox or ass which had vrnt tk committed the trespass (Tosaf.) . V. however, Rashi infra s.v. .');">⁴</span>

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