अर्जुन
In plain words
Arjuna said: You are the Supreme Brahman, the supreme light, the supreme purifier—the eternal divine Puruṣa, the primal Deity, unborn and all-pervading.
Word for word
The supreme Brahman, the supreme light, the supreme purifier [are] You; [they call You] the eternal Puruṣa, divine, the first God, unborn, all-pervading,
The commentators
Bhagavadgītābhāṣyam
यथोक्तां भगवतः विभूतिं योगं च श्रुत्वा अर्जुन उवाच —
परं ब्रह्म परमात्मा परं धाम परं तेजः पवित्रं पावनं परमं प्रकृष्टं भवान् । पुुुरुषं शाश्वतं नित्यं दिव्यं दिवि भवम् आदिदेवं सर्वदेवानाम् आदौ भवम् आदिदेवम् अजं विभुं विभवनशीलम् ॥ १२ ॥
In plain words
Having heard the Lord describe his own glory and his yoga in just this way, Arjuna spoke —
Supreme Brahman, the supreme Self, the supreme abode, the supreme light — pavitram: what purifies; paramam: the highest of all — this is you. Puruṣa, everlasting, eternal, divine — divyam: existing in heaven. Ādidevam: existing at the beginning of all the gods, and so the first god of them all. Unborn. Vibhum: whose very nature is to pervade everything.
Close to the Sanskrit
Having heard the glory and the yoga of the Lord, as described, Arjuna said —
Supreme Brahman, the supreme Self, the supreme abode, the supreme light — 'pavitram': purifying; 'paramam': pre-eminent — you are. 'Puruṣa, everlasting, eternal, divine' — 'divyam': existing in heaven; 'ādidevam': existing at the beginning of all the gods, hence the primal god; unborn; 'vibhum': one whose nature is to pervade.