Manusmriti

siva.sh/manusmriti/8/353

तत्समुत्थो हि लोकस्य जायते वर्णसङ्करः । येन मूलहरोऽधर्मः सर्वनाशाय कल्पते ॥ ३५३ ॥

sanskrit

For by (adultery) is caused a mixture of the castes (varna) among men; thence (follows) sin, which cuts up even the roots and causes the destruction of everything.

english translation

tatsamuttho hi lokasya jAyate varNasaGkaraH | yena mUlaharo'dharmaH sarvanAzAya kalpate || 353 ||

hk transliteration by Sanscript