法苑珠林 4.63

4.63

According to the Lokotpatti-sūtra: The Buddha told the monks, 'If non-Buddhists come and ask you, "By what cause and condition is there this sound in the sky?", you should reply, "By three causes and conditions striking against one another, sounds issue forth from the cloud-masses in the sky. What are the three? First, because the wind element within the clouds strikes and contacts the earth element, sound issues forth. Second, because the wind element within the clouds strikes and contacts that water element, sound issues forth. Third, because the wind element within the clouds strikes and contacts that fire element, sound issues forth. Why is this? Just as when tree branches rub against one another fire issues forth, this is also like that."' (According to the sūtras, thunder is of many kinds: there are thunder-chariots and thunder-drums that spirits and deities beat with mallets or strike with their hands; hence common speech calls them 'heavenly drums'. Among them, those who possess much evil and sin are struck dead by thunderbolts, visibly receiving their retribution.)