Bhashya
इदानीं समस्तस्यैव आरण्यकस्य योऽर्थ उक्तः, स समु- च्चित्य अस्यां कण्डिकायां निर्दिश्यते, एतावान्समस्तारण्य- कार्थ इति ।स वा एष महानज आत्मा अजरः न जीर्यत इति, न विपरिणमत इत्यर्थः ; अमरः- यस्माच्च अजरः, तस्मात् अमरः, न म्रियत इत्यमरः ; यो हि जायते जीर्यते च, स विनश्यति म्रियते वा ; अयं तु अजत्वात् अजरत्वाच्च अविनाशी यतः, अत एव अमृतः ।यस्मात् जनिप्रभृतिभिः त्रिभिर्भावविकारैः वर्जितः, तस्मात् इतरैरपि भावविकारै- स्त्रिभिः तत्कृतैश्च कामकर्ममोहादिभिर्मृत्यूरूपैर्वर्जित इत्येतत् ।अभयः अत एव ; यस्माच्च एवं पूर्वोक्तविशेषणः, तस्माद्भय- वर्जितः ; भयं च हि नाम अविद्याकार्यम् ; तत्कार्यप्रतिषेधेन
In plain words
Now the whole meaning of this entire forest-treatise gets gathered up and set down, whole, right here — this much is the sum of it all. 'He is this vast, unborn Self': undecaying means it never ages, never even changes. Undying — because it never ages, it never dies either: that is all 'undying' means. Anything that is born and ages eventually falls apart or dies; but this Self, never born, never aging, cannot perish — and that is exactly what makes it immortal. It stands free of birth, aging, and death, and free too of everything those three produce in us — desire, action, delusion — each one just another face of death. That is what it means to be fearless: this Self already carries every one of those qualities, so nothing is left in it for fear to attach to. Because fear itself is nothing but a product of not knowing who you are — and once that not-knowing is undone...
Close to the Sanskrit
Now, whatever meaning has been stated for the entire Āraṇyaka is gathered together and pointed out in this section: 'this much is the sum meaning of the entire Āraṇyaka.' 'He, verily, is this great, unborn Self' — 'ajaraḥ' [undecaying] means: does not age, that is, does not undergo transformation. 'Amaraḥ' [undying]: because it is ajara [ageless], therefore it is amara — 'does not die' is the meaning of amara. For whatever is born and ages, that perishes or dies; but this Self, because of unborn-ness and agelessness, is imperishable — for that very reason it is amṛta [immortal]. Because it is free from the three modifications beginning with birth, therefore it is also free from the other three modifications, and from those produced by them — desire, action, and delusion, which are in the form of death: this is the meaning. 'Abhayaḥ' [fearless]: for that very reason; and because it is already characterized as stated, therefore it is free from fear; for fear is indeed a product of ignorance — by the negation of that product...