That One Verse-6

Original in Sanskrit:

को अ॒द्धा वे॑द॒ क इ॒ह प्र वो॑च॒त्कुत॒ आजा॑ता॒ कुत॑ इ॒यं विसृ॑ष्टिः।
अ॒र्वाग्दे॒वा अ॒स्य वि॒सर्ज॑ने॒नाथा॒ को वे॑द॒ यत॑ आब॒भूव॑॥६॥

Joel P. Brereton’s translation:

Who really knows? Who shall here proclaim it? –
from where was it born, from where this creation?
The gods are on this side of the creation of this world.
So then who does know from where it came to be?

Raimundo Panikkar’s translation[i]:

Who really knows? Who can presume to tell it?
Whence was it born? Whence issued the creation?
Even the Gods came after its emergence.
Then who can tell from whence it came to be?

John Muir’s translation[ii]:

Who knows, who ever told,
from whence this vast creation rose?
No gods had then been born—
who then can e'er the truth disclose?

A. L. Basham’s translation[iii]:

But, after all, who knows, and who can say
Whence it all came, and how creation happened?
the gods themselves are later than creation,
so who knows truly whence it has arisen?

Max Muller’s translation:

Who knows the secret? who proclaimed it here,
Whence, whence this manifold creation sprang? -
The gods themselves came later into being. -
Who knows from whence this great creation sprang?

Ralph T.H. Griffith’s translation:

Who verily knows and who can here declare it,
whence it was born and whence comes this creation?
The Gods are later than this world's production.
Who knows then whence it first came into being?

Putting It Together:

This verse asserts the total mystery of the underlying That One of the cosmos.

No one knows about the cosmic source. Even Gods emerged after the emergence of the cosmos. Who then can tell from where it came? It will stay a mystery.