Had He Not Sinned, He Would Not Have Begotten Offspring
35) Had Adam brought offspring from the Garden of Eden, they would not perish for many generations, and the light of the moon, the light of Malchut, would never have darkened. Everyone would be living forever, and even the upper angels would not be able to match them in light, brightness, and wisdom, as it is written, “He created him in the image of God.” But because he caused the sin and went out from the Garden of Eden, making offspring outside the Garden of Eden, they did not exist in the world because they were not as they should be.
36) How could they beget offspring in the Garden of Eden? After all, had the evil inclination not been drawn on him and he sinned, he would exist alone in the world and would not bear offspring. Likewise, had Israel not sinned and drew on themselves the evil inclination after the reception of the Torah, they would not bear offspring in the world, and other generations would not have come to the world. Thus, the power of the coupling comes only because of the evil inclination, and without the evil inclination, there are no offspring.
37) Had Adam not sinned, he would not have begotten offspring from the side of the evil inclination. Instead, he would have born offspring from the side of the holy spirit, since now he is bearing offspring only from the side of the evil inclination. And because the offspring of the sons of men [people] are all from the side of the evil inclination, they are unsustainable and cannot exist because the Sitra Achra has mixed with them.
38) But had Adam not sinned and was not driven out from the Garden of Eden, he would have made offspring from the side of the spirit of the Holy of Holies, like the upper angels, and they would live for many generations, as it is above. In other words, there are two couplings: 1) a spiritual coupling, for the angels; 2) a coupling of Yesodot for the souls.
When it is said that they need the evil inclination, it is only for the coupling of Yesodot, and not for a spiritual coupling, which comes from the side of the spirit of holiness. Because he sinned and begot sons outside of the Garden of Eden—and was not rewarded with begetting them from the Garden of Eden—they did not exist or even strike roots in this world until Noah came and entered the ark. From the ark came forth all the generations of the world, and from there they spread to all four directions of the world.