Jocasta responds to the messenger’s story by becoming terribly upset, and then begging Oedipus to stop asking questions. SPOILER ALERT for those who have not read or seen “Oedipus Rex”. The messenger reveals that Oedipus has been adopted by the other king, and this convinces Oedipus that he needs to dig deeper into what is going on.
This comes to light as Jocasta has become convinced that the prophecy they were trying so hard to spoil has come true. Though she doesn’t want Oedipus to know the truth, she cannot stop him from asking his questions and poking around. She begs him to stop, regardless, because she wants this to stay secret. It would be quite upsetting to Oedipus to know the truth.