So what is the severity of the sin of Mishkav Zachur (homossexualism)?

It is written regarding the creation of Adam and Chava: Vayeva­rech otam vayikra et shemam Adam, “He blessed them, and called their name Adam [man]” (Bereshit 5:2). Torah is very clear to reveal that G-d called them ‘both’ Adam. In this way, He established that the spiritual nature of a human being is only completed in the world through the union of the ‘two distinct human aspects’, to wit, the masculine (corresponding to the active spiritual force and of expansion), and the feminine (corresponding to the passive spiritual force and of restriction). These spiritual forces embodied in the human being – and that exhibit such opposing functions – when united in the sanctified manner, form a ‘well balanced physical-spiritual pair’. This means a single being mirroring his origen in one common soul before its descent to this world and division into sexes. In fact, through this balance, flow all Divine blessings to the couple; and the whole world benefits from this most pleasing of unions in Shamayin. And as it is written, “When a couple lives in accordance to Torah law, the forces of Creation – the letters Yud and Hei from the holy Tetragram – reside with them. Then, in time, they become the image of the holy forces of Creation” (Tikunei Zohar, Tikun 10b). And it is also written that, “Who is incomplete below [i.e., not married] remains incomplete on high [i.e., spiritually]… And Ya’acov [the perfect patriarch]...alo, until his marriage was not complete” (Zohar I:150a, Vayetze).

Now, our Sages, all of blessed memory, have openly cautioned us: Kedoshim tihiyu hevu persuhim min ha-arayot u-min ha-evera, “Distance yourself from the illicit relations and from sin” (Rashi at the beginning of Parashat Kedoshim). And “of all isurei ha’arayot, only regarding the avon [sin] of Mishkav Zachur the Torah uses twice the word Toeva [Vayikra 18:22]. The Talmud explains that Toeva is Toe Hu Ba, which means that ‘he is making a mistake in this’… That is, ‘this’ is against human nature! It is the type of avon that exists only to challenge G-d. It is something that comes from the anger which feeds this abominable rebelliousness” (R’ Moshe Feinstein z”l, Teshuvah, Chelek 4 siman 115). And the Torah is also quite clear regarding the grave punishments of these forbidden unions, including that which occurs to the person committing these transgressions after he dies. The mekubal, HaRav Yehudah Fatiyah zt”l, the greatest student of the Ben Ish Hai, in his Sefer Minchat Yehudah describes his many conversations with tormented ruchot (spirits) which commited these abominations in life. They relate with terror the severity of their spiritual punishments! After all, not only from this transgression’s zera levatalah the sitra achra gets nourished and demoniacal beings are brought to life, but also each drop of semen spilled in vain implicates on the destruction of potential (unborn) children, which become imprisoned in the clutches of the klipot. Moreover, the ejaculated semen in a domain ‘absolutely improper’ deflowers these poor souls in a most perverse and horrible manner! Contrary to an union between man and wife which fulfills the mitzvah of procreation and gives the fruits of children y”h, if oral sex occurs in this sin, chaz v’shalom, then the only thing fulfilled are the spiritual deaths of the children which are as if “swallowed” in this most merciless abomination! Yet, regarding these rebellious ones, all members of the Erev Rav, it is written: “They all alike have broken the yoke, and burst the bonds… a wolf… shall destroy them… because their transgressions are many, and their apostasies are great” (Yermiyah HaNavi 5:5-6). Additionally: “The wicked with their sins pollute both themselves and the Sanctuary [i.e., they contaminate the earth], and bring a ruach rah [an unclean spirit] upon themselves; but in time to come G-d will purify Israel and remove from them the unclean spirit” (Zohar III:54a, Metzora). This ruach rah is the wicked Nebuchanetser, “who was deprived of his kingdom and he dwelt with the beasts of the field, his human countenance was taken away from him and from that day he did not bear the impress of a man” (Zohar II:125b, Mishpatim) – and was only to bear the image of a wolf! And as it is known, “Nebuchanetser used to tear the flesh of a live rabbit and eat it” (Eicha Rabah 2:14), and Kabbalah says that, “He who has homosexual relations is reincarnated as a rabbit” (the Ari”zal, Sha’ar HaGilgulim, Hakdamah 22, end).

Each and everyone who is involved in this most grievous of sins must use all of his kochot ha-nefesh (spiritual forces) to do teshuvah and implore Hashem’s mercy.