Reference for Sanhedrin 109:7
א"ל אם אינו ענין להעראה דכתיבא גבי אחות אביו ואחות אמו דלא צריכא דהא איתקש להעראה דנדה תניהו ענין להעראה דבהמה
apply its teaching to the first stage of bestiality [as being punishable].<span class="x" onmousemove="('comment',' In respect of one's paternal or maternal aunt, Scripture states: And thou shalt not uncover the nakedness of thy mother's sister, nor of thy father's sister: for he uncovereth his near kin. (Lev. XX, 19). The word for 'he uncovereth' (Heb. he'erah [H]) is understood as meaning the first stage of sexual intercourse, and this verse teaches that this is a culpable offence. But this teaching is superfluous, for in the preceding verse the same is taught of a niddah, which serves as a model for all forbidden human sexual intercourse. Hence the teaching, being redundant here, is applied to the first stage of bestiality. V. p. 368, n. 7. ');"><sup>7</sup></span>