Reference for Sanhedrin 109:2

דרש רב נחמן בר רב חסדא באשה שני משכבות ובבהמה משכב אחד

R. Nahman, son of R. Hisda stated in an exposition: In the case of a woman, there are two modes of intimacy, but in the case of a beast, only one.<span class="x" onmousemove="('comment',' The reference is to bestiality. If a woman allows herself to be made the subject thereof, whether naturally or not, she is guilty. But if a man commits bestiality, he is liable only for a connection in a natural manner, but not otherwise. Thus Rashi. Tosaf., more plausibly, explains it thus: If one commits incest or adultery with a woman, whether naturally or not, guilt is incurred; but bestiality is punishable only for a connection in a natural manner, but not otherwise. ');">²</span>

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