Musar su Salmi 119:37

For this reason our Sages of blessed memory (Avodah Zarah 20a) erected a protective fence forbidding a man from gazing upon anything that is liable to bring him to sin. For instance, he is forbidden from gazing at women and girls lest he be guilty of wasting seed. This is what King David had in mind when he wrote, “Avert my eyes from seeing vanity, cause me to live in Your ways” (Tehillim 119:37). The numerical value of the word shav (שוא), “vanity,” is 307, represented by the letters ש"ז (shin zayin), which is also the acronym for the term, shichvas zera, “semen.” (Dovid prayed that his eyes should not behold anything that could lead to shichvas zera.) This is a bold hint. It seems to me further that because Lilis and her cohorts are called “pangs of vanity” (shav) and also “pangs of death,” as is mentioned several times in the Zohar (1:12b; 2:33a), therefore David prayed, saying, “Cause me to live in Your ways.” That is, he asked to be influenced by the side of life and not the side of death, Heaven forbid.

In the second chapter we commented on the terrible punishment awaiting the man who wastes his seed. Concerning this Dovid HaMelech wrote, “Avert my eyes from seeing vanity, cause me to live in Your ways” (Tehillim 119: 37). It seems to me that this verse was a prayer that he be saved from gazing at forbidden sights, such as women, so that he would not defile himself at night, for the word “vanity” — שו"א — has the same numerical value as the acronym for seed, שז. Dovid HaMelech pleaded that the cohorts of the demon Lilis, who are known as Keri, not appear to him, for they cause a man to waste his seed at night. Since a child can be conceived from every droplet, wasting seed is considered akin to murdering those droplets with one’s own hands. Thus, one who wastes seed is under the sway of the Sitrah deMosah, the Side of Death. This is why Dovid requested, “Cause me to live in Your ways.” That is, he prayed to be under the sway of the Sitrah DeChayei, the Side of Life, and thereby to be saved from wasting seed. It is mentioned in the Zohar (Part II, 263) that there is an angel appointed over those who waste seed. It has in its charge thousands upon thousands of accusers and demons and destructive angels, all of whom cause a person to be defiled. Then they take the droplet that the man wasted and bring it on High, causing the mark of the covenant on his body to become enslaved to the Aspect of Impurity. Woe to the man who causes holiness to become enslaved to impurity!