Bhagavad Gita 18.20
That knowledge which sees the One Indestructible in all beings, the One Indivisible in all separate lives, can be truly called Pure Knowledge.
सर्वभूतेषु येनैकं भावमव्ययमीक्षते।अविभक्तं विभक्तेषु तज्ज्ञानं विद्धि सात्त्विकम्॥sarvabhūteṣu yenaikaṃ bhāvamavyayamīkṣate|avibhaktaṃ vibhakteṣu tajjñānaṃ viddhi sāttvikam||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).