 
“asaavaadityo brahma” :The  Sun is the icon of Brahman
INTRODUCTION
The first chapter of this Upanishad brought forward the idea  of yoga and knowledge as the effective methods of perceiving the inmost Self  hidden in the body. In this chapter prayer and various disciplines of yoga are  indicated for God Realization where prayer also is to be oriented towards the  nature of Reality as the goal.  Before  going into the yoga aspect the seven introductory Mantras of this chapter  invoke the Sun God, Savitr or Savita.
Of all the phenomenal objects, the sun is regarded with the  greatest wonder, admiration and awe. In the Vedas the sun is described as the  chief symbol of Brahman - asaavaadityo brahma. The Gayatri prayer is  directed to the Purusha dwelling in the sun. Natural sunlight is the  light of the Spirit. (Note: For a detailed exposition on the sun worship the  reader may refer to the author’s article entitled ‘Sun Worship - Suryopanishad’. http://www.esamskriti.com/essay-chapters/Sun-Worship-~-Suryopanishad-1.aspx 
The purport of this chapter is: ‘May the Sun first direct  our minds to the Supreme Self? Next, may he direct the cosmic forces which  control the sense organs to withdraw their powers from external objects?  Lastly, may he direct our understanding from worldly thoughts to the Self dwelling  within the body so that we may contemplate the Knowledge of Atman’?
THE  TEXT
PRAYER  TO THE SUN
Mantra 1
yuñjānaḥ prathamaṃ manas tatvāya savitā dhiyaḥ / 
    agner jyotir nicāyya pṛthivyā  adhy ābharat // 2.1 // 
May the sun,  at the commencement of yoga, join our minds and other organs to the Supreme  Self so that we may attain the Knowledge of Reality? May He, also, support the  body, the highest material entity, through the powers of the deities who  control the senses. 
The initial part  of the prayer to the Sun starts with an appeal to unite our minds and other  organs (five sense organs and five organs of action) with the Supreme self.  Among the organs, the mind is the leader which acts as a channel for knowledge  and initiates actions based on that knowledge. It functions like a charioteer  for controlling the wild horses of sense organs. All the calamities of life are  the result of weakness of mind. The prayer is “O Savita, it is your power alone  that is expressing through mind and organs and there is no other power besides.  So, be gracious, restrain the power from dissipating through mind and organs  and centralize that power within my body and organs for Knowledge of the  Self.”. 
This prayer is  in accordance with the nature of reality which will tranquilize the mind of the  seeker who will be anchored in Atman and undisturbed meditation will take  place. Thus this prayer indicates the seeker’s surrender to the power of all  the powers which will be later shown as Brahman itself.
In Vedanta the  physical body represents the five elements and the sense organs are presided  over by different deities symbolically representing the different aspects of  the all pervading Consciousness. Adi Sankara comments “May the Sun take our  thoughts away from external things in order to concentrate them on the Supreme  Self and transmit to our organ of speech and other organs that power which  lightens all objects and which inheres in Agni and other deities who control  the various organs. Through the grace of the Sun we shall attain success in  yoga”.
The natural  power of the mind and organs is to perceive external objects. As long as they  perceive the external objects the Self remains beyond our vision. Therefore the  prayer is for their control and turning inward so that their energy is not  dissipated. The 1st chapter told us that Brahman alone is real and  all else is illusory or unreal. The seeker may find obstacles in his way to put  this idea in practice in real life conditions. The main obstacle is the  outgoing nature of the mind and sense organs which results in total absence of  concentration. By praying to Savita, the Sun, the symbol of cosmic energy, the  extrovertness of the mind is controlled, redirected inward and gets focused.  The Sun is the power of all powers, Brahman with Shakti, the power of all the  Devatas.
Mantra 2
yuktena manasā vayaṃ devasya savituḥ save / 
    suvargeyāya śaktyā // 2.2 //  
Having received the blessings  of the divine Sun and with minds joined to the Supreme Self, we exert  ourselves, to the best of our power, toward meditation, by which we shall  attain Heaven (Brahman).
By the blessings of the sun, the mind gets fixed on Atman  and the powers of the deities who control the sense organs. Thereby, the body  is strengthened. The Supreme Self or Brahman is called heaven here because it  alone is the nature of absolute Bliss and in which all other joys are included.  With the mind controlled we are under the command of the divine Sun so that we  may have strength for attaining heaven or Brahman. Thus the purport of the  Mantra is ‘let us, through meditation and by grace of Savita, strive for that  Brahmananda which is the real joy itself and whose mere sparks are the worldly  joys’. 
Mantra 3
yuktvāya manasā devān suvar yato dhiyā divaṃ / 
    bṛhaj jyotiḥ kariṣyataḥ savitā prasuvāti tān // 2.3 // 
May the Sun  bestow favor upon the senses and the mind by joining them with the Self, so  that the senses may be directed toward the Blissful Brahman and may reveal, by  means of Knowledge, the mighty and radiant Brahman. 
The Sun is  prayed for turning our minds and the sense organs inward. Let the organs  withdraw from the sense objects and turn towards the Self. Unless we turn our  minds inward and re-direct the course of our thoughts from the external world  we cannot know our Self. Once the mind and the sense organs become strong and  refuse to be swayed by the external attractions and distractions, we become fit  for the experience of Brahman. Our prayer is to prepare the body, mind and  intellect in such a way that we can attain Self-Knowledge.
We may note that  these prayers indicate the stages of spiritual evolution in the seeker. First,  it was for stilling the outgoing mind and organs. Now the prayer is that they  may not slip-back to the worldly ways again. 
Mantra 4
yuñjate mana uta yuñjate dhiyo viprā viprasya bṛhato vipaścitaḥ / 
    vi hotrā dadhe vayunāvid eka in mahī devasya savituḥ pariṣṭutiḥ // 2.4 // 
It is the  duty of those Brahmanas who fix their minds and senses on the Supreme Self to  utter such lofty invocations to the divine Sun, omnipresent, mighty and  omniscient. For He, all-witnessing and non-dual, is the dispenser of  sacrifices. 
After  reiterating the necessity for the prayers to make the mind inward, this Mantra  makes a reference to the learned sages who have been able to unite their minds  and organs with the Self. They offer abundant praise to the Sun as  all-pervading and all-knowing, all-witnessing and non-dual, who has granted  them their prayers to bestow them Self-Knowledge and unite them with the Self.