अथ यत्रैतदस्माच्छरीरादुत्क्रामत्यथैतैरेव रश्मिभिरूर्ध्वमाक्रमते स ओमिति वा होद्वा मीयते स यावत्क्षिप्येन्मनस्तावदादित्यं गच्छत्येतद्वै खलु लोकद्वारं विदुषां प्रपदनं निरोधोऽविदुषाम् ॥ ८.६.५ ॥
atha yatraitadasmāccharīrādutkrāmatyathaitaireva raśmibhirūrdhvamākramate sa omiti vā hodvā mīyate sa yāvatkṣipyenmanastāvadādityaṃ gacchatyetadvai khalu lokadvāraṃ viduṣāṃ prapadanaṃ nirodho’viduṣām || 8.6.5 ||
5. Then when a person leaves the body, he goes upward with the help of these rays. If he dies while meditating on Om, his going up is assured; otherwise not. In the amount of time it takes his mind to move from one thought to another he can reach the realm of the sun. The sun is the gateway to Brahmaloka. Those who known the meaning of Om and think of it at the time of death enter Brahmaloka, but those who are ignorant of it have no chance of entering.
Atha, then; yatra, when; etat, this [person]; asmāt śarīrāt, from this body; utkrāmati, leaves; atha, then; etaiḥ eva raśmibhiḥ, by these rays; ūrdhvam ākramate, is carried upward; saḥ, he; om iti, by meditating on Om; vā ha ut mīyate, he surely goes up; vā, or [i.e., otherwise not]; yāvat, in the time that; manaḥ kṣipyet, the mind moves; tāvat, in that time; saḥ ādityam gacchati, he goes to the realm of the sun; etat vai, that [sun]; lokadvāram khalu, is the gateway [to the world of Brahman]; viduṣām prapadanam, for those who know [this Om] it is the entrance; nirodhaḥ aviduṣām, for the ignorant, entry is barred.
Brahmaloka. Those who know the meaning of Om and think of it at the time of death enter Brahmaloka, but those who are ignorant of it have no chance of entering.
What happens to a person when he dies? If he is a good person and has been meditating on Om, at the time of death he will try to meditate on Om in the heart. In Hinduism, it is the practice for religious people to die thinking of God. Here the Upaniṣad suggests meditation on Om.
Then when the dying person leaves the body, he quickly goes through the sun rays to the realm of the sun. How quickly? As quick as the mind can move. Suppose we think of someone who lives very close to us. Then we think of someone in England, or somewhere else far away. That is how fast the mind can move. Similarly, that is how fast it takes for a person to reach the sun.
The Upaniṣad says that the sun is the door to Brahmaloka. If you have meditated on your oneness with Om, then you go through this door to Brahmaloka. But what if a person is not religious and does not think of God or Om at the time of death? Then that door is closed for him. He cannot enter within.
Vedānta says, you are the architect of your own fate. A good person will have a good world to go to. And if he knows his true nature, he will go right to Brahmaloka. But those who still have desires are not free. They must stay in lower regions to wait for their rebirth.