GEN485 Know that Cain was evil and of the serpent, [R. Eleazar said: ‘When the serpent injected his impurity into Eve, she absorbed it, and so when Adam had intercourse with her she bore two sons—one from the impure side and one from the side of Adam, and Abel bore a resemblance to the higher form and Cain to the lower.  Hence it was that their ways in life were different. It was natural, too, that Cain, coming from the side of the angel of death, should kill his brother. He also adhered to his own side, and from him originate all the evil habitations and demons and goblins and evil spirits in the world.’ R. Jose said: ‘Cain was the nest (Kina, a play on the word Cain) of the evil habitations which came into the world from the impure side’ Zohar I, 54a, Soncino trans., Vol. I, p. 172) yet it was said to him: ‘If thou doest well [this verse], shall it not be lifted up.” Do not think that there is no hope for you because you belong to the evil side. This is false. Behold, if you do well you can root yourself in the secret of Repentance, removing yourself to that place, according to the secret of the good that is rooted there. For the root of every Supernal bitterness is sweet and he could have entered by way of the root to become good.  Consequently, man turns his evil deeds themselves into good so that his intentional sins become good deeds. [In Rabbinic teaching repentance out of love has the effect of converting even premeditated sins into merits, v. Yoma 86b].  For behold, the sinful deeds which he committed were prosecutors from the Left Side. When he returns in perfect repentance he causes those deeds to enter and be rooted above. Now all those prosecutors are not annihilated but they become better and rooted in the holy just as Cain was told he could be good. Behold, if Cain had repented and rectified his sins then the sin of Adam by which Cain (the unclean nest) was born, would have been accounted to him for merit, according to the secret of ‘the son brings merit to the father.’ However, he did not desire to repent. Therefore, all the Left Side draws its sustenance from there. But all its branches are destined to become sweet and they will be perfect once again. This is for the reason we have given: that man roots himself in the secret of evil and renders it sweet and brings it into the good. Therefore, man purifies the evil inclination and brings it into the good so that it becomes rooted above in the holy. This is the high degree of repentance which he who follows should ponder on each day and repent in some measure each day so that all of his days will be spent in repentance.  CORDOVERO 88-9