Divine intervention in Oedipus Rex takes more of an indirect form than is often the case in Greek tragedy, and provides the background against which the action unfolds. Apollo has already deemed what must happen, and yet both Oedipus and his parents arrogantly seek to avoid the fate that the god of oracles has so decreed. In doing so, they insult Apollo, failing to pay due respect to both him and his power.
A glimpse of the gods' implacable wrath comes through Pythia, the so-called Delphic Oracle, priestess of Apollo. She tells Creon—sent to Delphi by Oedipus—that the deadly plague ravaging Thebes is an expression of divine displeasure over the murder of Laius, Oedipus's birth father. Little does Oedipus know it, but he's the murderer in question, and it's his actions that have inadvertently led to the gods' terrible vengeance. Everything that happens in the play has thus been triggered by divine intervention in the sense that the gods have decreed what must be, and yet a number of characters, most notably Oedipus himself, have sought to defy the express will of the gods and so are punished through their actions.