Suetonius Quote

A few months before the murder [of Domitian] a raven perched on the Capitol and croaked out the words: "All will be well!" – a portent which some wag explained in the following verse:
There was a raven, strange to tell,
Perched upon Jove's own gable, whence
He tried to tell us "All is well!" –
But had to use the future tense.

The Twelve Caesars - Domitian