अव्ययः पुरुषः साक्षी क्षेत्रज्ञोऽक्षर एव च ॥ १५ ॥पूत आत्मा यस्य सः पूतात्मा, 'केवलो निर्गुणश्च' इति श्रुतेः ।गुणोपरागः स्वेच्छातः पुरुषस्येति कल्प्यते ।परमश्चासावात्मा चेति परमात्मा कार्यकारणविलक्षणो नित्यशुद्धबुद्धमुक्तस्वभावः ।मुक्तानां परमा प्रकृष्टा गतिर्गन्तव्या देवता पुनरावृत्त्यसंभवात्तद्गतस्येति मुक्तानां परमा गतिः; 'मामुपेत्य तु कौन्तेय पुनर्जन्म न विद्यते' इति भगवद्वचनम् ।नास्य व्ययो विनाशो विकारो वा विद्यत इति अव्ययः, 'अजरोऽमरोऽव्ययः' इति श्रुतेः ।पुरं शरीरं तस्मिन् शेते इति पुरुषः ।'नवद्वारं पुरं पुण्यमेतैर्भावैः समन्वितम् ।व्याप्य शेते महात्मा यस्तस्मात्पुरुष उच्यते' इति महाभारते ।यद्वा, अस्तेर्व्यत्यस्ताक्षरयोगात् आसीत्पुरा पूर्वमेवेति विग्रहं कृत्वा व्युत्पादितः पुरुषः, 'पूर्वमेवाहमिहासमिति, तत्पुरुषस्य पुरुषत्वम्' इति श्रुतेः ।अथवा पुरुषु उत्कर्षशालिषु सीदतीति, पुरूणि फलानि सनोति ददातीति वा, पुरूणि भुवनानि संहारसमये स्यति अन्तं करोतीति वा पूरणात्सदनाद्वा पुरुषः ।'पूरणात्सदनाच्चैव ततोऽसौ पुरुषोत्तमः' इति पञ्चमवेदे ।साक्षादव्यवधानेन
In plain words
Avyaya (the Imperishable), Puruṣa (the Supreme Person), Sākṣin (the Witness), Kṣetrajña (the Knower of the Field), Akṣara (the Indestructible), and Pūtātmā (the Pure-Souled). Pūtātmā is one whose very essence is pure, as scripture declares: 'Alone and without attributes.' Any apparent coloring by the material gunas is merely imagined through the Lord's own free will. Paramātmā is the supreme self, entirely transcending cause and effect, eternally pure, conscious, and free. It is the highest destination of the liberated, from which there is no return, as Lord Krishna affirms: 'Having attained me, O son of Kuntī, there is no further birth.' Avyaya is one in whom no waste, destruction, or change ever occurs, as scripture calls him 'ageless, deathless, imperishable.' Puruṣa is so named because he reposes within the city of the body, as the Mahābhārata states: 'Pervading the nine-gated city, the great soul reposes within, and therefore is called Puruṣa.' Alternatively, the word is derived from the root as, meaning to exist from the very beginning, as scripture affirms. Or he is Puruṣa because he excels among the eminent, bestows abundant fruits, or dissolves the many worlds at the time of cosmic rest. As the fifth Veda declares: 'Because he fills and because he dwells, therefore he is Puruṣottama.' Sākṣin means one who perceives directly without any intervening medium.
Close to the Sanskrit
Avyayaḥ, Puruṣaḥ, Sākṣī, Kṣetrajñaḥ, Akṣaraḥ, and Pūtātmā. Pūtātmā: whose self is pure, by the śruti 'Alone and without gunas'. The assumption of quality-attachment by the puruṣa is imagined through his own will. Paramātmā: and supreme is this self, distinct from cause and effect, having the nature of eternal purity, consciousness, and freedom. The supreme, excellent destination of the liberated, since return is impossible for one who has attained that—hence Paramā Gati; the divine saying is 'Having attained me, O Kaunteya, there is no rebirth'. Avyaya: of this there is no waste, destruction, or modification, by the śruti 'Ageless, deathless, imperishable'. Puruṣa: in the city (the body) he lies, thus Puruṣa; 'Having pervaded the nine-gated city, auspicious with these states, the great soul lies, therefore he is called Puruṣa' in the Mahābhārata. Or else, derived by analyzing with inverted letters of the root as: 'He existed in the beginning', by the śruti 'That puruṣa's puruṣa-ness'. Or because he sits among eminent ones, or because he grants many fruits, or because he destroys many worlds at dissolution, from fulfilling or dwelling, Puruṣa: 'From fulfilling and from dwelling, therefore he is Purottama' in the fifth Veda. Sākṣāt without intermediary