Khandogya-Upanishad: Second Prapathaka, Fifteenth Khanda

I. The mists gather, that is the hinkara; the cloud has risen, that is the prastava; it rains, that is the udgitha; it flashes and thunders, that is the pratihara; it stops, that is the nidhana. That is the Vairupa Saman, as interwoven in Parganya, the god of rain.

2. He who thus knows the Vairupa as interwoven in Parganya, obtains all kinds of cattle (virupa), he reaches the full life, he lives long, becomes great with children and cattle, great by fame. His rule is, “Never complain of the rain.”