Wasting semen is a Torah prohibition according to all authorities. Punishment is death at the Hand of Heaven. (Niddah 13A) While in several places, the Zohar indicates that there is no tshuva for this transgression, the meaning is that ordinary repentance, stemming from the fear of punishment, does not suffice, but that a course of higher repentance, or tshuva m’ahava, stemming from a great love of G-d, is needed. (Baal HaTanya, Letter of Tshuva, Ch. 4)
The Talmud compares masturbation with adultery: (See Niddah 13A and B)
“Rabbi Eliezer said, It is written, ‘Your hands are full of blood.’ (Yishayahu, 1:15) This refers to people who arouse themselves with their hands. The words of the commandment, You shall not commit adultery, imply not with your hand and not with your foot.”
“Rabbi Yochanan said: Anyone who wastes his seed is liable to the death penalty, as is written, ‘And the thing which he did was evil in the sight of the L-rd, and He slew him also.’ (Bereshit, 38:10)
“Rabbi Yitzhak and Rabbi Ami said: It is as if here were a murderer, as is written, ‘Slaughterers of children in the valleys, under the clefts of the rocks.’” (Yishayahu, 57:5)
“Rabbi Asi said: It is as if he were an idol worshipper.”
The halacha as stated in the “Kitzor Shulchan Oruch,” states:
- It is forbidden to discharge semen in vain. This is a graver sin than any other mentioned in the Torah. (Shulchan Oruch, Even HaEzer, 23:1) Those who practice masturbation and cause the issue of semen in vain, not only do they commit a grave sin, but they are under a ban, concerning which it is said, “Your hands are full of blood,” (Yishayahu, 1:15) and it is equivalent to killing a person. See what Rashi wrote concerning Er and Onan in the Portion of Vayeshev (Bereshit, Ch. 37) that both Er and Onan died for the commission of this sin. Occasionally, as a punishment for this sin, children die young, G-d forbid, or grow up to be delinquent, while the sinner himself is reduced to poverty.
- One is forbidden to cause an erection, or to think about women. If a lascivious thought comes to one spontaneously, he should divert his attention to a subject of Torah. Lewd thoughts prevail only in a mind devoid of wisdom. A man should be extremely careful to avoid an erection. Therefore he should not sleep on his back with his face upward, or on his belly with his face downward, but sleep on his side, in order to avoid it. Two bachelors should not sleep together. One should not watch animals, beasts, or fowl copulate. It is also forbidden to ride on an animal without a saddle.
- It is forbidden to hold the membrane while urinating. If one is married and his wife is in town and she is ritually clean, it does not matter, for since he has the possibility, he will not indulge in lustful thoughts or become stimulated; but it is nevertheless a matter of piety to avoid it. When not for the purpose of urinating, the above is forbidden by the law.
- At supper, one should neither eat nor drink excessively, nor eat any foods that tend to heat the body, such as fat meat, cheese, eggs, or garlic. Neither should one drink a beverage that tends to heat the body, for all of these things cause the commission of this sin.
In summary, we can see from the warnings of the Torah, from the admonishments of the Talmud, from the exacting prohibitions of Jewish Law, and from the inner understandings of the Zohar and the Kabbalah, that Shmirat HaBrit is indeed the foundation upon which all of life is based.