Bhagavad Gita
1.39

कुलक्षये प्रणश्यन्ति कुलधर्माः सनातनाः | धर्मे नष्टे कुलं कृत्स्नमधर्मोऽभिभवत्युत ||३९||

kula-kṣhaye praṇaśhyanti kula-dharmāḥ sanātanāḥ dharme naṣṭe kulaṁ kṛtsnam adharmo'bhibhavaty uta

Translation

With the destruction of the dynasty, the eternal family traditions are vanquished, and thus the rest of the family becomes involved in irreligion.

Interpretation

Arjuna now makes a social argument: the destruction of families destroys the 'eternal family traditions' (kula-dharma). When dharmic traditions collapse, irreligion (adharma) floods in. This is a genuine social concern, but Arjuna is applying peacetime ethics to a situation that has already been corrupted by Duryodhana's adharma.