BG: 8 is about Akśara Parabrahman (imperishable Brahman). The 9th verse is about the attributes of God to meditate at the time of death.
kaviṁ purāṇaṁ anu śāsitāram aṇor aṇīyāṁsam anusmared yaḥ
sarvasya dhātāram acintya-rūpam āditya-varṇaṁ tamasaḥ parastāt
kaviṁ-omniscient; purāṇaṁ - ancient; anu śāsitāram – ruler; aṇor aṇīyāṁsam – smaller than atom; anusmared – meditates upon; yaḥ - one who
sarvasya dhātāram – supporting all, acintya-rūpam – whose form is inconceivable, āditya-varṇaṁ - luminous like sun; tamasaḥ parastāt – transcending material/physical world
One who meditates on the omniscient, ancient, the controller, minuter than atom, supporter of everything, with inconceivable form, shining like sun, and beyond darkness/material world.
Similar verses in Upanishads
In the (kṛṣṇa pakṣa yajur veda) Kaṭha Upaniṣad (1.2.20):
aṇoraṇīyān mahato mahīyān ātmasya jantornihito guhyāṁtamakratuḥ paśyati vītśhoko dhātuḥ prasādān mahimānam ātmanaḥ
1-II-20. The Self that is subtler than the subtle and greater than the great is seated in the heart of every creature. One who is free from desire sees the glory of the Self through the tranquillity of the mind and senses and becomes absolved from grief.
In (kṛṣṇa pakṣa yajur veda) Śvetāśvatara Upaniṣad (3.8)
वेदाहमेतं पुरुषं महान्तं आदित्यवर्णं तमसः परस्तात्
तं एव विदित्वाति मृत्युमेति नान्यः पन्था विद्यतेSयनाय ||
vedāham etaṃ puruṣaṁ mahāntam ādityavarṇaṁ tamasaḥ parastāt |
tam eva viditvāti mṛtyum eti nānyaḥ panthā vidyate 'yanāya || 3.8 ||
I know the great Puruṣa, who is resplendent, like sun and beyond darkness. Only by knowing Him does one pass over death; there is no other way to the Supreme Goal.
This Mantra is very popular in the daily Vedic chanting of Puruṣa Sūktam.
The Brahma Purana states: The Supreme Being is kavi or all knowing. He is the seer of everything because He knows all things.
