Kauṣītaki Upaniṣad 1.2.2

1.2.2

teṣāṃ prāṇaiḥ pūrvapakṣa āpyāyate /

2. Then he said: 'Those who, verily, depart from this world—to the moon, in truth, they all go. During the earlier half it thrives on their breathing spirits (prāṇa); with the latter half it causes them to be reproduced. This, verily, is the door of the heavenly world—that is, the moon. Whoever answers it, him it lets go further. But whoever answers it not, him, having become rain, it rains down here. Either as a worm, or as a moth, or as a fish, or as a bird, or as a lion, or as a wild boar, or as a snake, or as a tiger, or as a person, or as some other in this or that condition, he is born again here according to his deeds (karman), according to his knowledge.