זוהר שמות — דף קיא ע”א

Two categories of women are vulnerable to the grip of the serpent's voice: one who does not properly observe the laws of menstrual purity, and one who withholds from her husband his conjugal right in order to torment him. When the serpent's voice mingles with the woman's voice, the evil force that emerges from the ephah (jar) encounters them and warms itself with them. This causes the evil spirit to enter the woman's womb, and the child born thereafter is exposed to Lilit's attack.