1.Dvidhaa vaa esha aatmaanaam bibharti ayam yah praano yaschaasaa Aadityotha dvau vaa etaasyaya panthaanaa antar bahischa ahoraatrenaitau vyaavartete, asau vaa aadityo bahiratmaa antaratmaa praanoto bahir aatmakyaa gatya antaraatmaat maano numeeyate gatir iti evam hyaahaatha yah kaschid vidvaan apahata paapmaakshaadyaaksho vadaata manaastan nishthaa avritta chakshuh so antaraatma - kyaa gatyaa bahir aatmanonumeeyate gatir ityevam ha aaha, atha ya eshontaraaditye Hiranmayah purusho yah pashyaatimaam hiranyavashat sa eshontare hrit pushkara evaashritonnam atti

The Self as a Being is conditioned by his prana, the vital energy inside the body, by his vision and experience of the Pratyaksha Bhaskara. Similarly, the path of discovering the Inner Self and the Supreme is similar, by discarding the material senses and thoughts as influenced by one’s mind and by total abstinence, thereby discovering the antaratma and by that awareness realising Paramatma. In other words, the Supreme as invisible in the solar globe needs to be realised from the earth by one’s interior lotus of the mortal heart as supported by Praana which in turn is sustained by food.

2.Atha ya eshontare hrit pushkare evaashritonnam atti sa eshognir divi shritah saurah kaalaakhoy - drishya sarva bhutaani annam attiti, kah pushkarah kim mayo veti, idam vaa va tat pushkaram yoyam aakaashosyemaas chatasro dishaash chatasra upadisho dalaa samsthaa aasam, arvaag vicharita etau praanaadityaa etaa upaasheetom iti etad aksharena vyaahritibhih saavitryaa cheti

The Self who enters the lotus of humanity into their heart consuming similar kind of food just as the heat of Surya Deva and enters the invisible Antaratma in the ‘daharaakaasha’ and the ‘kaalachakra’ or the wheel of eternal time and the ‘Akaasha’, the external sky as created by Paramatma.
The lotus is indeed the space within and above, comparable to a tree which has as its leaves the Dasha Dishas or ten directions viz. uttara or north, east or purva, dakshina or south, paschim or west, ishanya or north-east, agneya or south east, nirruti or south west, vayavya or north west, urthwa or upper region. Praana, the vital energy and Surya Deva are parallels moving near each other. Now let the Self be revered with the utterances of Bhur- Bhuvah- and Swah along with the syllable OM- AUM -along the prayer of Savitri/ Gayatri.

3. The symbol of AUM is the Paramartha Satyam - the Eternal Truth of the Formless and the Form.
Dve vaava Brahmano rupe murtaan cha aurmurtan cha;atha yan murta tad asatyam, yad amurtam tad Brahma, tajjyotih, yaj jyotih sa aadityah, sa vaa yesha ityedam atmaabhavat, sa tredhaatmaanam vyakurutaa, Aum iti, tisro maatraa etaabhih sarvam idam otam protam chaivaasmeeti, evamhyaahaiad vaa aaditya Aum ityevam dhyaayata aatmaanam yunjeeteti

Paramatma is realisable in two ways: one with a form and another the formless. Now the Brahman with a Form is stated as unreal or an empirical or by way of observation while He who is Real is the Permanent and Everlasting Truth which indeed is in Supreme Radiance and in a way like the Pratyaksha Bhaskara from whom the three folded AUM is derived. The entire Universe as woven like the warp and weft around Him who comprises the three letters and the analogy thus is that the solar orbit of Surya Deva be worshipped and meditated upon as AUM. In sum, the Formed Paramatma is the Form and the Reality is Formless Avyakta-Shashwata-Sarvavyaapi-Anantam-Ajam-Avyayam, that is The Unknown-Everlasting-All Pervasive-Endless-Birthless-Undiminishing!

4.Athaanyatraapi uktam, atha khalu ya udgeethah sa pranavo yah pranavah sa ugeetha esha pranavaa iti/ Evam hyaahodgeetam pranavaakhyaam pranateraram bhaa rupam vigata nidram vijaram, vimrityum, tripaadam, tryaksharam punah panchadhaa jneyam nihita guhaayaam ityevam hyaadhorddhva mulam tripaad brahma shaakhaa aakaashaa vaayuvagni udaka bhumyaadaya ekoshvaattha naamaaitad brahmaitasyaitat tejo yad asaa aadityah AUM iti etad aksharasya chata, tasmaad AUM iti anenaitad upaaseetaajasram iti ekasya sambodhaeti evam hyaaha/ Etad evaaksharam punyam, etad evaaksharam param, etad evaaksharam jnaatvaa yo yad icchati tasya tat

It is stated elsewhere [see Chhandogya Upanishad I.v.1 to be quoted hence] that Udgita or what is recited as a hymn is pranava or Omkara while what Omkara is Udgita. Now Udgita,  the pranava swarupa, is not only the prime performer of sacrificial tasks but the manifestation of the antaratma, the three footed, three lettered AUM, the five folded panchabhutas as represented in the panchendriyas of the beings in srishti. Indeed, Paramatma is comparable to a massive fig tree as resplendent like Bhaskara whose essential radiance is what the syllable AUM represents! Hence the magnificence of the Supreme.

Chhandogya Upanishad vide I.v.1-6 is relevant: I.v.1: Atha kalu udgitah sa pranavo yah pranavah sa udgita iti asau vaa udgita, esha pranava, Om iti hyesha swaraaneti/
Pranava and Udgita are just the same. These are also the forms of Surya Deva for brightness and Praana, the vital energy for bestowing Life; Sun is ‘considered’ to be ever on the move, yet constant and the syllable AUM too is all pervasive and this is what Udgita is all about!

I.v.2 Etamu evaaham abhayagaa – sisham tasmaan mama twam ekoseeti ha Kaushitakih putram uvaacha, rasmistwam paryaavartayaad bahavo vai te bhavishyantiti adhidaivatam/
Maharshi Kaushitaki asked his son to ponder over the innumerable sun rays sincerely so that he would be blessed with several bright and virtuous sons; this is in the context of divinities.
I.v.3 Athaadhyaatmam ya evaayam mukhyah praanastam udgitam upaaseetomiti hesha swaranneti/
Referring to meditation and introspection on the individual plane in reference to the body, this should indeed be on the praana in the mouth organ, which would need be recited in Udgita and significantly enough addressed to the pranava mantra AUM; the similarity on the divine plane too as in respect of Surya Deva as applicable to the vital force.

I.v.4: Etamu evaaham abhyaagaasisham, tasmaan mamatwam ekoseetii ha Kausheetakih putram uvacha, praanaastwam bhumaanam abhigaayataad bahavo vaime bhavishyanteeti/

Kaushitaki told his son that he should always worship prana, the vital energy in his physique as present in various forms so that the son would beget several sons, since the Maharshi was blessed only with a single son! Indeed, the vital force in the mouth is as important as Surya Deva is and hence would bestow several sons as his many rays.

I.v.5: Atha khalu ya Udgitah sa Pranavah, yah Pranavah sa Udgita iti hotrshadanaad haivaapi durudgeetam anusaamaaharateeti anusmaaharatiti/

Maharshi Kaushitaki asserted that Udgita was pranava and vice versa and even if the oblations were poured defectively and wrongly out of tune with the Udgita, it would mean no harm and the resultant cure of the bodily ailment would surely be accomplished and the desires of the karta of the Udgita should be fulfilled!

Rig Veda vide X.90 - 3-4 stanzas are relevent : Etaavaanasya mahimaato jyaayaancha Puurushah, paadosya vishvaa bhutaani tripaadasyaamritam divi/ Tripaaduurthva udait Purushah paadosyehaa- bhavat punah, tato vishvang vyakraamatsaashanaanashane abhi/

The entire universe is far bigger than the virat purusha; this immortal Master is the Supreme Energy to the universe and the various beings as sustained by food. Of His three feet, three lokas got manifested, one sustained by food and others otherwise.