यदा भूतपृथग्भावमेकस्थमनुपश्यति।तत एव च विस्तारं ब्रह्म सम्पद्यते तदा॥
yadā bhūta-pṛthag-bhāvam eka-stham anupaśyatitata eva ca vistāraṃ brahma sampadyate tadā
Word by word
The verse says
When he sees that the separate states of beings all rest in one, and spread out from that one — at that point he reaches Brahman.
In plain words
Resting in one, and spreading out from it. Both halves.
Not that the differences are false. That they rest somewhere and come from there.
Tadā — then, at that point. The verse names a moment.
Where you've felt this · in family life
You look at a photograph of four generations at a wedding and see the same nose on a great-grandmother and a two-year-old. Nobody in the picture is a copy of anybody. The resemblance does not make them less themselves, and you cannot unsee it once you have seen it.
Going deeper
Seeing unity without losing the differences is what this verse asks for, and both halves are stated.
The separate states of beings rest in one — and spread out from it. If only the first half were said, this would be a claim that difference is illusion. The second half says the diversity comes from there too. The many are not a mistake about the one.
Chapter 11 described exactly this when Arjuna saw the whole world in one place and still divided into all its kinds.
For a reader this is the difference between a real recognition and a flattening. Anybody can say we are all one; it costs nothing and usually means the speaker has stopped paying attention to particular people. What is described here leaves everybody exactly as particular as they were, and that is harder to arrive at and worth more when you do.