Jaiminīya Upaniṣad Brāhmaṇa 3.10

"Indeed, sir, your father considered him an udgātṛ," he said.
And Prācīnaśāla they know as the one who was their chosen udgātṛ;
concerning that, he did not know.

They said: "Run after Kāṇḍviya!"
They ran after him.
They made Kāṇḍviya the udgātṛ, and Prācīnaśāli the brahman priest.

Looking down upon him, he said: "Thus this brāhmaṇa did not tire of idle talk.
He does not seek the fine [truth] of the sāman."
Thus he surpassed him.

Now, when the father pours him into the womb as semen, Āditya pours him into the womb as semen.
He rules over his death there.

And when the father pours him into the womb as semen, then he is born from that and from breath;
for when breath enters the poured semen, then it comes into being.

And when they consecrate him, Agni indeed pours him into the womb as semen.
He rules over his death there.

And whichever vaisarjanīya oblation the adhvaryu offers, he is born from that and from the metres.

And when they place him, departed from this world, upon the funeral pyre, the Moon indeed pours him into the womb as semen.
And he rules over his death there.

And when they place him, departed from this world, upon the funeral pyre, and whatever sprinkling waters these are, he is born from them and from breath;
for breath is the waters.

Such a knowing udgātṛ carries that sacrificer across the death that is Āditya with the syllable 'om', across Agni with 'speech', across Vāyu with 'hum', and across the Moon with 'bhā'.

Across these deaths the udgātṛ carries himself and the sacrificer by means of the sāman, by this syllable 'om', by breath, and by that Āditya.

Regarding this there is this verse:
"Both their eldest and their youngest, both their son and their father— / the one god entered into the mind; he was born first, and he is within the womb."

As to what was referred to in verse, it is this very person who is covered within, by this very syllable om, by breath, by that sun.
Fifth khaṇḍa in the second anuvāka.
The second anuvāka is concluded.