And the L-rd saw that the wickedness of man was great in the earth
"And the L-rd saw that the wickedness of man was great in the earth, and all the desire of the thoughts of his heart was only evil all of the day," (Bereshit, 6:5.)
Rabbi Yehuda quoted the verse, "For thou art not a G-d who has pleasure in wickedness, nor shall evil (ra) dwell with Thee," (Tehillim, 5:5.)
He explained: Come and see - someone who cleaves to the evil inclination and pursues it, not only does he defile himself, but he is led to pollute himself further, as has already been stated. For the wickedness of mankind was great (in the generation of Noach) and all kinds of evil was committed, but the measure of their guilt was not complete until they wasted their blood (semen) upon the ground. Who are these people who corrupted their way on the earth? We know by comparing two verses. Here, it is written, "Only evil (ra) all of the day," and in another verse, "And Er, Yehuda's firstborn, was evil (ra) in the sight of the L-rd," (Bereshit, 38:7.)
Said Rabbi Yosi: Isn't evil (ra) the same meaning as "wickedness" (resha)? No. A man is considered wicked if raises his hand to strike his neighbor, even if he doesn't touch him, as it is written, "And he said to the wicked one (rasha), why will you strike your fellowman?" He is called wicked even though the future tense of the verb indicates that he had not yet done any physical harm.
But, evil (ra) refers only to a person who corrupts his way and pollutes himself and the earth (by spilling semen in a sinful manner.) This lends force and added strength to the impure spirit which is called "ra" as it is written, "only evil (ra) all the day." This person will not be allowed to enter the celestial palace, nor gaze upon the Shechinah, for by this sin the Shechinah is driven from the world.
How do we know this? From Yaacov. When the Shechinah departed from him, he thought that perhaps his sons were blemished in this manner, and because of them the impure spirit had grown stronger in the world, even blemishing the moon and diminishing its light. If you wonder how this can be - the reason is that this sin pollutes the Temple (and drives the Shechinah from the world.) If this is what caused the Shechinah to leave Yaacov, how much more so does it apply to any man who corrupts his ways and defiles himself, thus adding strength to the spirit of impurity. Therefore, when a man defiles himself in this manner, he is called evil (ra.)
Behold, when a man defiles himself, the Holy One, Blessed Be He does not visit him with blessing. Rather, he is subject at all times to visitations of the spirit called "ra."