法苑珠林 63.19

63.19

又大方等大雲經云。佛言。若有國土欲祈雨者。六齋之日。其王應當淨自洗浴供養三寶。尊重讚歎稱龍王名。善男子四大之性可令變易。誦持此呪天不降雨。無有是處。是經典中有神呪故。為眾生故。三世諸佛悉共宣說。

Furthermore, the *Mahāvaipulya-mahāmegha-sūtra* states: The Buddha said, "If there is a country that wishes to pray for rain, on the day of the six fasts, its king should purely bathe himself, make offerings to the Three Jewels, show reverence, utter praise, and call upon the names of the nāga kings. Good son, the natures of the four great elements may be altered, but that one should recite and uphold this incantation and heaven not bring down rain—that is impossible. Because there are divine spells in this scripture, for the sake of sentient beings, the Buddhas of the three periods of time have all proclaimed it together."