Bhagavad Gita Chapter 1 Verse 43

Gita 1.43

DoshaeH, etaeH, kulaghnaanaam’, varnsankarkaarkaeH,
Utsaadhyante, jaatidharmaH, kuldharmaH, ch, shaashvataH ||43||

Translation: (EtaeH) these (varnsankarkaarkaeH) that create mixture of castes (doshaeH) faults (kulaghnaanaam’) destroyers of family (shaashvataH) ancient (kuldharmaH) laws of family (ch) and (jaatidharmaH) laws of the community (utsaadhyante) become destroyed. (43)

Translation: By these evil deeds of the destroyers of the family, that give rise to mixed castes, the ancient laws of family and the laws of community become destroyed.