There were many prophets in olden times, claiming to speak in the name of God, interpreting events in the lives of people and nations as signs of God's anger or judgement. But they were not always speaking the mind of God. Today's first reading places the great Jeremiah against another prophet who presumed to speak in the name of God and foretell good news for the people. Jeremiah reminds him that it's easy to "read" wars and disasters as being interventions of God in human affairs, but a prophet of peace can only be recognized as one truly sent by the Lord when his word comes true.
Hananiah's "good news" didn't happen: in fact he was leading the people astray with false hopes, and Jeremiah had to tell him so, and tell him that he'd die within a year.
Whenever disasters and tragic events happen, there are always people who "read" these things as judgements of an angry God. Sometimes good people begin to doubt or wonder about these things. Jeremiah didn't immediately criticize and condemn that other prophet - maybe he too wasn't sure, and was waiting for the Lord's inspiration. But in the end he spoke strongly: "Listen carefully Hananiah: the Lord has not sent you".
It's true that Christians are called to be the Lord's priests and prophets. But let's not presume too easily that we know God's mind or purpose in the events of our world.
Lord, we are witnesses for God's peace, prophets of the God who is Love.