Kabbalah Kidung Agung 8:9: Zohar & Reshit Chokhmah

and he contemplated in wisdom both what was above and what was below. But once he sinned his prosopa diminished, wisdom departed from him, and he could survey only the affairs of his body. He then begat offspring partaking both of the higher and of the lower nature, but the world was not settled by either of them until Adam begat a son called Seth,¹Sheth = foundation. by whom the world was made complete.¹Al. with whom the world was planted. v. Mid. r. Num. 14, 12; Cant. 8, 9.

Also in the Midrash they explained the verse “every man with his sword on his thigh” (Song of Songs 8:9) relating to being cautious of the Brit, “because of dread in the night” that they are cautious of sin, which is prevalent at night-time.