Plain text of Aitareya Upanishad · Second Adhyaya
Fourth Khanda
A person's three successive births
2.4.1 In a man, verily, the seed of life is at first an embryo. That which is the seed is the vigor gathered from all the limbs. When he places this in a woman, then he begets it. This is one's first birth.
2.4.2 It comes into being with the woman, just as a limb of her own. Therefore it injures her not. She nourishes this child that has come to her.
2.4.3 She, being a nourisher, should be nourished. The woman bears him as an embryo. In the beginning, indeed, the father nourishes the child and from birth onward. While he nourishes the child from birth onward, he thus nourishes his own continuation, for the continuation of these worlds; for thus are these worlds continued. This is one's second birth.
2.4.4 This person is put in his place for pious deeds. Then, having done his work, having reached his age, he deceases. So, deceasing hence indeed, he is raised again on the Day of Resurrection. This is one's third birth.
2.4.6 So he, knowing this, being righteous and departing from this body, obtains all righteous desires in the heavenly Garden, and has eternal life, yea, eternal life!