The gemara¹ tells us that wherever Abaye and Rava disagree, the halachah follows Rava, except in the six cases known by the mnemonic יע"ל קג"ם ("Ye'al Kegam"),² which are the signs of six laws in which the halachah follows Abaye instead. Why are these cases different?
The Arizal³ says that within Lot's soul was contained Rus Ha'moaviyah and Naamah Ha'amonis who came about through his two daughters. The soul of Rava was contained within Naamah Ha'amonis. R' Yosef Greenwald of Papa⁴ explained that the reason the halachah does not follow Rava in these cases is because that during the time Lot was held captive among the kelipos, they retained a slight hold over the soul of Rava, and therefore, in the six cases of Ye'al Kegam, the halachah does not follow him.
¹ Baba Metzia 22b.
² This stands for יאוש שלא מדעת abonnement without the owners awareness, עדים זוממין, false witnesses, לחי העומד מאליו, a lech that stands by itself, קידושין שלא נמסרו לביא, kiddushin that are not given to cohabitation, גלוי דעתא בגיטא clarification of intention regarding a get, ור אוכל נבילות להכעיס, a renegade who eats unkosher meat in defiance of the Torah.
³ Shaar Hagilgulim, Hakdama 36, p. 48a.
⁴ In his sefer Vayechi Yosef, Parashas Lech Lecha.