First, it highlights Oedipus' reputation for wisdom and sound judgment. Creon acknowledges that Oedipus is not given to speaking lightly or without careful thought. This establishes Oedipus as a credible and respected figure, making his eventual downfall all the more tragic.
Second, the line foreshadows Oedipus' downfall. By suggesting that Oedipus is not prone to making mistakes or speaking carelessly, Creon inadvertently sets the stage for Oedipus' tragic error in judgment. This irony adds to the dramatic tension of the play and builds suspense as the audience awaits the revelation of Oedipus' hamartia.
Finally, the line also serves to underscore the tragic irony of Oedipus' situation. Oedipus is a wise and just ruler who is ultimately undone by his own ignorance and pride. Creon's statement, while intended as a compliment, inadvertently highlights the tragic flaw that will lead to Oedipus' downfall.