Bhagavad Gita Chapter 1 Verse 42

Gita 1.42

SankarH, narkaay, ev, kulaghnaanaam’, kulasya, ch,
Patanti, pitarH, hi, eshaam’, luptpindodakkriyaH ||42||

Translation: (SankarH) mixture of castes (kulaghnaanaam’) destroyer of family (ch) and (kulasya) family (narkaay) to take to hell (ev) is only (luptpindodak) secret bodily pleasure/sex; from male-female’s seminal fluid and seed (kriyaH) from act (eshaam’) their (pitarH) descendents (hi) also (patanti) decline. (42)

Translation: Mixture of castes is responsible for taking the destroyer of the family and the family itself to hell. From the secret act of bodily pleasure, their descendents from the male-female’s seminal fluid and seed also decline.