Bhagavad Gita · 13.31

यदा भूतपृथग्भावमेकस्थमनुपश्यति।तत एव च विस्तारं ब्रह्म सम्पद्यते तदा॥

yadā bhūta-pṛthag-bhāvam eka-stham anupaśhyati tata eva cha vistāraṁ brahma sampadyate tadā

When one perceives the diverse existence of beings as rooted in one source, and sees their expansion from that source alone — then one attains Brahman.

— Bhagavad Gita 13.31

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