Why have the priests come to altar in book Oedipus Rex?

In Sophocles' play "Oedipus Rex", the priests come to the altar because of a plague that is devastating Thebes. The people are suffering and the city is in despair, so the priests turn to the gods for guidance and help. They seek the advice of the oracle at Delphi, who tells them that the plague will only be lifted if they find and punish the killer of Laius, the previous king of Thebes. The priests bring this message back to the city and appeal to Oedipus, the current king, to help them find the murderer and restore order to Thebes.