This argument seems strong to me and sufficiently plausible for us to conclude that if God were to decide that from this day forward He is going to will to send rain at the utterance of some word pronounced by someone, then that word, once uttered, would be just as properly a cause of the rain brought about by God at its utterance as heat is a cause of heat. And this seems altogether true. For a creature has nothing except from God's will alone, which grants it to the creature freely and contingently.

gabriel biel, whether the sacraments of the new covenant are effective causes of grace, p.3-4