Why is teiresias reluctant to tell oedipus his prophecy ?

Teiresias was described to be a cranky old fellow. Despite being blind, it was believed that he see things better than how other view them. During their first encounter, Oedipus was furious because Teiresias did not intend to tell the king about Laius' murderer. 

On another occasion, Teiresias did not tell Oedipus about his knowledge that would be able to save Thebes because he believed that "everything that's going to happen will happen anyway"