Bhagavad Gita · Vibhuti YogaChapter 10, Shloka 20 (10.20)

Shankaracharya. guḍākā nidrā tasyāḥ īśaḥ guḍākeśaḥ, jitanidraḥ ity arthaḥ, ghanakeśa iti vā — the one who has conquered sleep, or the one with thick hair; aham ātmā pratyagātmā nityaṃ dhyeyaḥ; tadaśaktena ca uttareṣu bhāveṣu cintyaḥ aham — I am the inner Self, always worthy of meditation; one who cannot do this should contemplate me in the forms that follow.

Acharya Ramanuja. sarveṣāṃ bhūtānām mama śarīrabhūtānām āśaye hṛdaye aham ātmatayā avasthitaḥ — all beings are my body, and I am the Self in their hearts; ātmā hi nāma śarīrasya sarvātmanā ādhāro niyantā śeṣī ca — the self means the support, controller and master of the body; with evidence from 15.15, 18.61 and Brihadaranyaka 3.7.15 (the Antaryami Brahmana).

Madhusudana Saraswati. He takes this verse as an instruction for meditation: ātmā caitanyānandaghanas tvayāhaṃ vāsudeva eveti dhyeyaḥ — meditate on me in the heart as the Self, a mass of consciousness and bliss. The address "Gudakesha" (conqueror of sleep) dhyānasāmarthyaṃ sūcayati — hints at the capacity to meditate. And evaṃ dhyānāsāmarthye tu vakṣyamāṇāni dhyānāni kāryāṇi — if such meditation is not possible, meditate on the glories that follow.

Shridhar Swami. sarvajñatvādiguṇair niyantṛtvenāvasthitaḥ paramātmā — the Supreme Self abiding as the controller, with qualities such as omniscience.

Abhinavagupta. An important warning: the purpose of first saying "I am the Self" is vyavacchedaṃ vārayati — to prevent a wrong limitation. Otherwise, hearing "among mountains I am the Himalaya", someone might think that only the Himalaya is the Lord and nothing else — then brahmadarśanaṃ khaṇḍitam abhaviṣyat, the vision of Brahman would be broken.