Hassidout sur Les Nombres 24:22

And behold in the [writings of] ARI, may his memory be blessed: Jethro was from the root of Cain. And it is explicit in Scripture that he is called Cain, [referring to the Kenite descendants of Jethro,] Nevertheless Cain shall be wasted (Numbers 24:22). And it is written [about a descendant of Jethro], Heber the Kenite had severed himself from Cain (Judges 4:11). And it is well-known that Cain was extremely evil, and that he transgressed the three sins that are the roots of all the sins, idolatry, sexual immorality, and murder: Idolatry in that he denied [God] and said, "There is no Judge and no judgement." Sexual immorality in that he had sexual relations with Abel's wife, who was the extra twin born with Abel. Murder, in that he killed Abel. Hence, Jethro — who was a reincarnation of Kain — was drawn by these earlier sins towards all evil and towards these three sins. And it is well-known that the sins of a previous incarnation literally draw one towards those sins. And this is [what is meant by], "one sin drags along another sin" (Avot 4:2). However, Jethro fortified himself against his nature and did the opposite: Corresponding to the sin of idolatry, [after] it caused him to be greatly drawn to it to the point that he did not leave over any idolatry that he had not worshiped, he fortified himself and separated from idolatry and announced this. Corresponding to the sins of sexual immorality and murder, it is found in [the writings of] Rabbi Chaim Vital that it is that he gave his daughter, Zipporah, to Moses, since she was the extra twin who was born with Abel, and he gave her over to Moses, who was the reincarnation of Abel. And so it is in the Midrash (Shemot Rabbah 27:1), "Eight matters are written in a derogatory manner regarding Esau that are written in a complimentary manner regarding Jethro. Regarding Esau it is written, They tormented women in Zion (Lamentations 5:11). Regarding Jethro it is written, He gave Zipporah, his daughter, [to Moses] (Exodus 2:21). And corresponding to his killing Abel, he sustained Moses, who was a reincarnation of Abel, as it is written, call him and let him eat bread (Exodus 2:20). And certainly had another man, who was not drawn towards idolatry, sexual immorality, and murder, done this, it would not have been such a novelty. But Jethro, who was drawn and powerfully pushed by the ancient sin but nevertheless fortified himself against his nature and fled from all of these things and did the opposite — that is a great novelty. And according to our words above, corresponding to his fleeing and pushing off [his] nature, he merited that the lock on his heart concerning that matter was torn and that his nature and the buffer and covering on his heart were pushed away. So he truly saw and heard what he had not heard before then.