Verse 2.2.1

आविः संनिहितं गुहाचरन्नाम महत्पदमत्रैतत्समर्पितम् ।
एजत्प्राणन्निमिषच्च यदेतज्जानथ सदसद्वरेण्यं परं विज्ञानाद्यद्वरिष्ठं प्रजानाम् ॥ १ ॥

āviḥ saṃnihitaṃ guhācarannāma mahatpadamatraitatsamarpitam |
ejatprāṇannimiṣacca yadetajjānatha sadasadvareṇyaṃ paraṃ vijñānādyadvariṣṭhaṃ prajānām || 1 ||

1. Bright, well-fixed, moving in the heart, great and the support of all; in him is all this universe centred, what moves, breathes and winks. Know this which is all that has form and all that is formless, which is to be sought after by all, which is beyond the reach of man’s knowledge, and the highest of all.

Shankara’s Commentary:

Com.—It is now explained how the akshara which is formless, could be known. Avihi, bright, shining as the percipient of sound, etc., according to the Sruti, “It shines through its conditions of speech, etc.” It is seen in the heart of all living beings appearing there with the attributes of seeing, hearing, thinking, knowing, etc. This Brahman shining is Sannihita, i.e., well seated in the heart. It is celebrated as guhacha- ran because it moves in the cavity in modes of seeing, hearing, etc. ‘Great’, because it is greater than all. Padam, reached by all, because it is the seat of all objects. How is it said to be great, etc? Because in the Brahman all this universe is centred as the various spokes are in the wheel-ring of the chariot. Ejat, moving, i.e., birds, etc; pranet, breathes, i.e., men, cattle, etc., having prana, a puna, etc; and ‘winks’, all that winks and all that winks not, from the force of the particle cha; this in which all is centred, know, O disciple, that that is your own atman; both sat and asat; for without it, sat and asat, that which has form and that which has not, i.e., the gross and subtle do not exist. Varenyam, covetable; because of all objects it is the only eternal entity. Param, distinct from, or, beyond; this is connected with the expression “knowledge of men” though remote; the meaning is that it is beyond the reach of wordly knowledge. Varishtham, the highest of all; because of all that is high, the Brahman is pre-eminently high, being free from all faults.