Reference for Sanhedrin 149:18
מנין לעשות למטה כלמעלה נאמר כאן זמה ונאמר להלן זמה מה להלן למטה כלמעלה אף כאן למטה כלמעלה ומה כאן למעלה כלמטה אף להלן למעלה כלמטה
Just as there, her daughter, her daughter's daughter and her son's daughter [are meant by zimmah], so here too her daughter, her daughter's daughter, and her son's daughter [are included in the punishment of burning decreed for incest with them]. Whence do we know that males are as females? 'Wickedness' [zimmah] is stated here, and also elsewhere; just as there, males are as females, so here too. Whence do we know that the lower is as the upper? 'Wickedness' [zimmah] is stated here, and also elsewhere: just as there, the lower is as the upper, so here too; and just as here the upper is as the lower, so there too.<span class="x" onmousemove="('comment',' This is explained in the Gemara. ');"><sup>14</sup></span>