In plain words
Undivided in beings, it appears as though divided. That which is to be known is the sustainer of beings, their absorber, and their source.
Word for word
Undivided, and yet in beings standing as though divided; and that knowable [is] the sustainer of beings, the devourer and the originator.
अविभक्तं च भूतेषु विभक्तमिव च स्थितम्भूतभर्तृ च तज्ज्ञेयं ग्रसिष्णु प्रभविष्णु च
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
किञ्च —
अविभक्तं च प्रतिदेहं व्योमवत् तदेकम् । भूतेषु सर्वप्राणिषु विभक्तमिव च स्थितं देहेष्वेव विभाव्यमानत्वात् । भूतभर्तृ च भूतानि बिभर्तीति तत् ज्ञेयं भूतभर्तृ च स्थितिकाले । प्रलयकाले ग्रसिष्णु ग्रसनशीलम् । उत्पत्तिकाले प्रभविष्णु च प्रभवनशीलं यथा रज्ज्वादिः सर्पादेः मिथ्याकल्पितस्य ॥ १६ ॥
In plain words
And further —
'Undivided' — and yet present in every single body, the way space is; it remains one, whole, unsplit. Among all living creatures it looks as though it has been divided up — but that is only because it is perceived through the medium of separate bodies, nothing more. 'Supporter of beings' means exactly that: it supports every being — that is what the object of knowledge is called during the time things simply continue on as they are. At the time everything dissolves, it is the one that absorbs, that takes everything back into itself. At the time everything arises, it is the one that brings everything forth — the way a rope gives rise to the false appearance of a snake.
Close to the Sanskrit
And what more —
'Undivided', and, in each body, like space, that [is] one. Among beings, [that is] among all living creatures, it stands as if divided, because it is perceived only in [each of the various] bodies. 'Bhūtabhartṛ' [means]: and it supports beings — that [is] the object of knowledge, [it is] 'bhūtabhartṛ' at the time of continuance. At the time of dissolution, [it is] disposed to devour, [that is] of the nature of devouring. At the time of origination, [it is] disposed to bring forth, [that is] of the nature of bringing forth — just as a rope and so on [is the substrate] of a falsely-imagined snake and so on.