Yajnad bhavati parjanyah [Bg 3.14].

[All living bodies subsist on food grains, which are produced from rain. Rains are produced by performance of yajna [sacrifice], and yajna is born of prescribed duties.] Let them chant Hare Krsna, and pani [water] will come from up, not from the ground. Otherwise Gita is false.

Srila Prabhupada, Room Conversation with Vrindavan De – July 6, 1977, Vrndavana