Bhagavad Gita 1.41
When irreligion spreads, the women of the house start to stray; when they lose their purity, adulteration of the lineage follows.
अधर्माभिभवात्कृष्ण प्रदुष्यन्ति कुलस्त्रियः।
स्त्रीषु दुष्टासु वार्ष्णेय जायते वर्णसङ्करः॥adharmābhibhavātkṛṣṇa praduṣyanti kulastriyaḥ|
strīṣu duṣṭāsu vārṣṇeya jāyate varṇasaṅkaraḥ||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).