If Krsna does not supply you this light, sunlight, you will die. But He does not charge anything. But because you are human being, you should try to repay: “Oh, Krsna is giving us so much facilities. Let me render some service unto Him.” This is Krsna consciousness. This is to acknowledge, “O God, You are so kind. You are giving so many things. So I have collected this fruit. It is Your fruit, I know. Still, please accept.”

From Srila Prabhupada’s lecture on Bhagavad-gita 4.1-2 — 9 May, 1969