3 There is no counterpart of him whose glory verily is great.
In the beginning rose Hiranyagarbha, etc. Let not him
harm me, etc. Than whom there is no other born, etc.
8 He hath attained unto the Bright, Bodiless, Woundless,
Sinewless, the Pure which evil hath not pierced.
Far-sighted, wise, encompassing, he self-existent hath
prescribed aims, as propriety demands, unto the
everlasting Years.
This passage is referring to the man who has realized the Atman, which is Brahman. Essentially, this is referring to the God-realized man, not God Himself:
6 The man who in his Self beholds all creatures and all things
that be,
And in all beings sees his Self, thence doubts no longer,
ponders not.
7 When, in the man who clearly knows, Self hath become all
things that are,
What wilderment, what grief is there in him who sees the
One alone?
You're forgetting the rest of the passage, which reads:
9 Deep into shade of blinding gloom fall Asambhûti's
worshippers.
They sink to darkness deeper yet who on Sambhûti are
intent.
10 One fruit, they say, from Sambhava, another from Asambhava.
Thus from the sages have we heard who have declared this
lore to us.
11 The man who knows Sambhûti and Vinâsa simultaneously,
He, by Vinâsa passing death, gains by Sambhûti endless life.
Right, a dying man's prayer to Agni:
16 By goodly path lead us to riches, Agni, thou God who
knowest all our works and wisdom.
Remove the sin that makes us stray and wander: most
ample adoration will we bring thee.
Likely the prayer is directed to Agni because they practiced (and most often still do) cremation rather than burial.
