Bhagavad Gita · 11.13

तत्रैकस्थं जगत्कृत्स्नं प्रविभक्तमनेकधा।अपश्यद्देवदेवस्य शरीरे पाण्डवस्तदा॥

tatraika-sthaṁ jagat kṛtsnaṁ pravibhaktam anekadhā apaśhyad deva-devasya śharīre pāṇḍavas tadā

There, in the body of the God of gods, Arjuna then saw the entire universe — with its many divisions — all standing as one.

— Bhagavad Gita 11.13

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)