What is the relationship between curse Oedipus lays upon murderer and statement that he speak idle words?

Oedipus lays a curse upon the murderer of Laius, stating that he will be punished by the gods and will never find peace. He also states that he speaks idle words, meaning that his words are not to be taken seriously. This is because he does not know who the murderer is and is simply expressing his anger and frustration.