Reference for Chullin 229:17

שילוח הקן ליתסר

Should not 'It and its young' be forbidden, since I have declared it to be abominable to you?<span class="x" onmousemove="('comment',' Cf. Lev. ibid. 28. If the dam and its young were both slaughtered in one day, that which was slaughtered last should be forbidden for all time and for all use; nevertheless it is established law that even though the law has been transgressed both animals are permitted; v. supra 78a.');">¹¹</span>

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