गोविन्द भाष्य (श्रील बलदेव विद्याभूषण - अचिन्त्यभेदाभेद वेदान्त ब्रह्मसूत्र भाष्य सटीक)

One who hears the Upaniṣads and understands the secret knowledge of the
Vedas travels to the Supreme Personality of Godhead. Of the person who knows
the person in the eye Upakośala Muni says arciṣam abhisambhavati (He attains the
realm of light). Because these two persons (he who knows the secrets of the Vedas
and he who knows the person in the eye) attain the same destination it must be
understood that the person in the eye is the Supreme Personality of Godhead.
Sūtra 17
anavasthiter asambhavāc ca netaraḥ
anavasthiteḥ—because the abode is not eternal; asambhavāt—because of being
impossible; ca—and; na—not; itaraḥ—anyone else.
(The person in the eye) is not anyone else (but the Supreme Personality of
Godhead) because (the others) do not stay always in the eye and because it
casnnot be them (according to the context).
Purport by Śrīla Baladeva Vidyābhūṣaṇa
These other persons cannot be the person in the eye because none of them stay
permanently in the eye and because non of them possess immortality or any of the
other qualities attributed to the person in the eye. The Supreme Personality of
Godhead is therefore the person in the eye referred to in this text.
Adhikaraṇa 5
The Internal Ruler is the Supreme Personality of Godhead
Introduction by Śrīla Baladeva Vidyābhūṣaṇa
Viṣaya: Bṛhad-āraṇyaka Upaniṣad 3.7.18 says:
yaḥ pṛthivyāṁ tiṣṭhan pṛthivyā antaro yaṁ pṛtivī na veda yasya pṛthivī śarīraṁ
yaḥ pṛthivīm antaro yam ayaty eṣa ta ātmāntaryāmy amṛtaḥ