Aitareya Upanishad

1. In a person, he first becomes an embryo. What the seed
is is energy {tejas), come together from all the limbs. One
carries a self in oneself (atman). When one sprinkles it in a
woman, one begets it. That is one’s first birth.

2. It becomes own self to the woman, just like a limb of
her own, so it does not harm her. She nurtures one’s self
when it has come here.

3. She, the nurturer, becomes one to be nurtured. The
woman carries the embryo. One nourishes the boy before
and after birth. When one nourishes the boy before and after
birth, one nourishes oneself {atman}. for the continuance of
the worlds: for so the worlds continue. That is one’s second
birth.

4. He, being one’s self, is set in one’s place for meritorious
actions. Then one’s other self, having done what was to be
done and reached his age, departs . Departing from here,
he is born again. That is one’s third birth.

5. It was said by the Rishi:

‘While in the womb I fully knew
The births of all the gods.
A hundred citadels of iron surrounded me.
A hawk, I flew out with speed.’

Vamadeva said that while lying in the womb.

6. Knowing this, from the break-up of this body he rose
upwards; he won in that heavenly world all desires; and he
became immortal, became immortal.