357. "You shall not uncover the nakedness of your father's sister..." (Vayikra 18:12). Rabbi Chiya opened the discussion saying, "And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness..." (Vayikra 20:17). We have learned that Adam lived apart from his wife for 130 years and did not beget children, since Adam did not want to copulate with his wife after Cain slew Abel. Rabbi Yosi taught that from the time death was decreed for him and all mankind, he has said, why should I beget children that will be destroyed? He immediately separated from his wife.
369. We have learned that after the passing of Cain and Abel, Adam returned to his wife. A different spirit enveloped him and he begot Seth. From this lineage, the righteous trace their line in the world. The Holy One, blessed be He, increased Chesed in the world, and with each was also born a female to populate the world, just as above, AS ZEIR ANPIN AND MALCHUT WERE BROTHER AND SISTER. The friends have established in the general Mishnah that it is written ABOUT THEM, "And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness... It is a disgraceful (Heb. chesed, it is confusing but the word chesed can mean disgraceful or kindness) deed" (Vayikra 20:17). Assuredly it is Chesed, for after Chesed rests, offspring and roots come out underneath upwards, and branches spread, MEANING ZEIR ANPIN AND MALCHUT. What was near moved away. Then the branches grew, ZEIR ANPIN AND MALCHUT, and came to join into one in a tree. This was in the beginning, in the concealed state of the world. It is written, "For I have said, the world is built by love (chesed)" (Tehilim 89:3). THEREFORE, from now on, people in this situation THAT MARRY THEIR SISTER "shall be cut off in the sight of their people" (Vayikra 20:17).