The meditator who meditate upon Īśvara with attributes, seeking only spiritual benefit is talked about. In saguna-brahma-upāsana, one imposes either pratima (image of the Lord) or pratīka (symbol) upon Īśvara. Here the symbol Om is used as the support for the omkāra-upāsana which is most of the Upanishad talked about. Next is the introduction of this omkāra-upāsana.
yadaksaram vedavido vadanti viśanti yadyatayo vītarāgāh | yadicchanto brahmacharya caranti tatte padam sangrahena pravaksye ||8.11|| I will tell you briefly about that end, which does not decline, about which the knowers of Veda talk about, which the renunciate, free from desire, enter, and desiring which people follow a life of study and discipline.
I will tell you briefly that brahman which is reached by omkāra-upāsana, which the knowers of veda talk about - vedavido vadanti. One who understand the teaching of veda, they know that the entire veda is revealing the nature of brahman as the central teaching. In Brhadāranyaka-upanisad (3-8-8), Yajñavalkya teaches Gārgi about aksaram brahma. He said, "It is not big, nor small, nor short, nor tall and thus, free from all attributes. Aksaram brahma is not an object, nor it is something to be gained in the usual sense. It is not to be experienced, but known".
viśanti yadyatayo vītarāgāh - people who give up other pursuits and they are free from desires to gain material benefits, dedicates their life to this brahman alone.
yadicchanto brahmacharya caranti - desiring to know which, people live a life of discipline in the presence of the teacher.
Now Lord Krsna briefly talks about the process of this omkāra-upāsana.
sarvadvārāni samyamya mano hrdi nirudhya ca |
mūrdhnyādhāyātmanah prānam āsthito yogadhāranām ||8.12||
omityekāksaram brahma vyāharanmāmanusmaran |
yah prayāti tyajandeham sa yāti paramām gatim ||8.13||
Closing all the gates of perception (sense organs), withdrawing the mind into the heart, placing his breath at the top of his head, being the one who remains holding (his breath) by yoga, chanting he single syllable Om, which is Brahman, giving up the body, the one who departs remembering Me, goes to the most exalted end.
anyacetāh satatam yo mām sarati nityaśah |
tasyāham sulabhah pārtha nitya yuktasya yoginah ||8.14||
Pārtha (Arjuna)! The one who has a mind that sees no other, who remembers Me, constantly, for that yogin who is always united with Me, I am easily gained.
tasyāham sulabhah - I am easily gained for them. There are so much preparation one should do to gain either self-knowledge here, or brahma-loka, but now Lord Krsna says that Īśvara is easy to gain. Any gaining or accomplishment requires effort, no matter how big or little it is. As long as something is different from you, effort is needed to gain it. Even after gaining it, effort to retain also must be there. The easiest gaining or even does't need effort to gain is my own self. Therefore the phrase "Īśvara is easy to gain" indicates that brahman which the meditator wishes to gain by upāsana is nothing different from one self. And when the qualification to understand this oneness is there, the knowledge just take place by itself, this is another meaning.
By achieving brahman, what does one accomplish?
māmupetya punarjanma duhkhālayamaśāśvatam |
nāpnuvanti mahātmānah samsiddhim paramām gatāh ||8.15||
Having reached me, the wise men do not gain another birth, which is the abode of misery and finite; they have reached the ultimate success.
ābrahma bhuvanāllokāh punarāvartino'rjuna |
māmupetya tu kaunteya punarjanma na vidyate ||8.16||
Arjuna! All the world (where beings exist) up to the world of Brahmaji are subject to return. However, having reached me, Kaunteya (Arjuna)! there is no rebirth.
When one gained self knowledge and be free in brahma-loka itself, it is said that one doesn't gain another birth here. Rebirth is said to be the abode of misery and pain, because from starting in the womb of mother till the time one got delivered to this world is full of pain and misery. Not to talk about the emotional and physical pain one needs to endure during the life in this world. Even if one gain a celestial body in heaven, it is also not eternal, as when one's punya is over, one will melt into another sphere of experience.
Even in brahma-loka, when the day of resolution come and one hasn't free oneself there, this jīva will also return to his/her circle of birth and death.
sahasrayugaparyantam aharyadbrahmano viduh |
rātrim yugasahasrāntām te'horātravido janāh ||8.17||
Those people who know about the day and night, know that a day of Brahmaji consists of one thousand yugas and a night (of Brahmaji) measuring one thousand yugas.
avyaktādvyaktayah sarvāh prabhavantyaharāgame |
rātryāgame pralīyante tatraivāvyaktasamjñake ||8.18||
At the beginning of the day, all things that are manifest arise from the unmanifest. At the beginning of the night, they resolve in that alone which is called unmanifest.
bhūtagrāmah sa evāyam bhūtvā bhūtvā pralīyate |
rātryāgame'vaśah pārtha prabhavatyaharāgame ||8.19||
Pārtha (Arjuna)! The same group of beings indeed (which), having repeatedly come into being necessarily dissolves when the night (of Brahmaji) comes. When the day comes, it necessarily arises.
We have a standard system to measure time in our modern world like year, decade, century etc. In veda we also has standard to measure the length of time of unmanifest to a manifest world. The existence of the world consists of four yuga, they are satya-yuga (1.728.000 years), tetra-yuga (1.296.000 years), dvāpara-yuga (864.000 years) and kali-yuga (432.000 years). One round of four of them which it self is called as one yuga here or kalpa. One day of brahmaji is equal to 1000 yuga. When the day of brahmaji started, all unmanifest come to manifest and stay on till the end of the day. When brahmaji's night begins, all the loka (sphere of experience) are destroyed, except brahma-loka. When we go to sleep, our world is dissolved so it is logical that when brahmaji goes to sleep, the entire creation is resolved into him except for brahma-loka itself. Then creation remains dissolved for the same length of time, and again it begins when brahmaji's day break. Brahmaji longevity is one hundred years and at the end of it, is the destruction of brahma-loka also. Therefore even for one who is successfully go to brahma-loka with this omkāra-upāsana, it is also not eternal.
Resolution is not total destruction, because creation itself is only from unmanifest, comes to manifest. This is totally make sense, because if every time new set of jīva is created at the beginning of creation, what is the determining factor for which jīva goes to what kind of body? If resolution means total destruction, then creation means Īśvara creates varieties of new jīva for his own amusement or for no purpose at all. Furthermore, śāstra enjoins certain actions and prohibition where one will gain punya and pāpa (karma). If karma in jīva's account get destroyed along with the jīva during resolution, they will not enjoy the result of their actions. Without karma and without any self-knowledge, jīva will get liberated at the resolution. Then both enjoin and prohibition from śāstra serve no purpose.
avaśah - indicates helplessness of jīva being caught in the cycle of creation and dissolution. Only through self-knowledge jīva can be free from this cycle of samsara.