Musar zu Schemuel II 7:14

The Shach [Sifsei Kohen by Rabbi Mordechai HaKohen] on Parashas Ki Teitzei (55a) writes as follows: It is stated, “When a man has two wives, one beloved and the other hated, etc.” (Devarim 21:15). This passage can be explained with reference to a man’s wife and the wicked Lilis. These are the two “wives.” And since only one man in a thousand is spared the sin of wasting seed the Torah warns that a man should at least guard that first drop. Thus the verse continues, “And the firstborn should be to the hated one [i.e., his real wife].” This is in order that “on the day that he bequeaths to his sons” — i.e., the day of death — he will be able to overcome all the demons, spirits and liliths born from those droplets of wasted seed, which the Zohar (1:54b) calls, the “plagues among Adam’s offspring” (II Shmuel 7:14). For when it is time for him to be buried these spirits will try to attach themselves to him but they will be unable to do so because his firstborn son will overcome them. This is the deeper meaning of the verse, “streams of water ran down from my eyes because they did not keep Your Torah” (Tehillim 119:136). Note that the verse does not say “because I did not keep Your Torah,” but “because they did not keep Your Torah.” That is, a man’s eyes will themselves shed tears because of the harm they caused through gazing. For the eye sees and the heart desires, such that all of a man’s deeds are caused by the vision of his eyes. This is what brings him to wasting seed. Tears, by contrast, are the rectification for wasting seed. For just as the seed originates in the brain, so do tears. Therefore a man must pray specifically with tears. He must also shed tears when he mourns for the destruction of the Holy Temple or for an upright individual who has died.