Responsa על ברכות 111:2

Regarding the Talmudic tale of Bar Haddaya (Berachot 56a:2), who when given a fee would interpret dreams positively, and when not paid, would interpret them as negative omens. It is also said there (ibid.) that Rava found a book that fell from his hands, and in it was written 'All dreams follow the mouth'. We are astounded by this and ask [in a dream] whether it is possible that heavenly decrees are affected by human interpretation. Is this meant to be understood literally, that dreams depend on their interpretation, for better or for worse? Or is it not to be understood this simple way, since heavenly decrees do not change? For Bar Haddaya himself was nothing but a dream interpreter, and why was it then written in his book that 'all dreams follow the mouth'?