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

bhedena—by the difference; enam—this; adhīyate—is read.
The ruler within is not a jīva because in both (recensions of the Upaniṣad) the
jīva is described as different from Him.
Purport by Śrīla Baladeva Vidyābhūṣaṇa
The word na (not) from the preceding sūtra should be understood in this sūtra
also. For the reasons already given it cannot be said that a jīva who is a great yogī
is the ruler within. Why? The sūtra answers hi, which means "because," ubhaye
(in both), which means "in both the Kāṇva and Mādhyandina recensions of the
Upaniṣad," enam (He), which means "the ruler within," bhedena adhīyate (is
described as different).
(The Kāṇva recension gives) yo vijñānam antaro yamayati (The
transcendental knowledge that rules within) and (the Mādhyandina recension,
gives) ya ātmānaṁ antaro yamayati (The Supreme Personality of Godhead who
rules within). In both readings is a clear distinction between the ruler and the
ruled. Therefore the ruler within is Lord Hari, the Personality of Godhead.
In the Subāla Upaniṣad the Kaṭhas say: pṛthivy-ādīnām
avyaktākṣarāmṛtāntānāṁ śrī-nārāyaṇo 'ntaryāmī (Lord Nārāyaṇa is the ruler
within the earth and other elements, within the unmanifested pradhāna, and
within the unchanging, eternal jīva).
The Brāhmaṇas say: antaḥ-śarīre nihito guhāyām (The Supreme Personality of
Godhead stays in the heart of the jīva), aja eko nityaḥ (The Supreme Personality of
Godhead is unborn, eternal, and one without a second), and yasya pṛthivī śarīraṁ
yaḥ pṛthivīm antare sañcaran yaṁ pṛthivī na veda (The earth is His body. He stays
within the earth. The earth does not understand Him, the Supreme Personality of
Godhead).
Adhikaraṇa 6
"Akṣara" is the Supreme Personality of Godhead
Introduction by Śrīla Baladeva Vidyābhūṣaṇa
Viṣaya: The Muṇḍaka Upaniṣad (1.1.5-6) says:
atha parā yayā tad akṣaram adhigamyate. yat tad adreśyam agrāhyam agotram
avarṇam acakṣuḥ-śrotraṁ tad apāṇi-pādaṁ nityaṁ vibhuṁ sarva-gataṁ su-sūkṣmaṁ
tad avyayaṁ yad bhūta-yoniṁ paripaśyanti dhīrāḥ