Source, in full
There is an ancient saying—Idleness / Is the world's curse: and I have heard a story / Out of old time, instructive. / King Matthew once, half-tipsy, put three fellows— / Three idle fellows—in a house to fatten; / And fate, or forethought, set the house on fire. / "Ah! see, the house is burning!" cried the first; / "If the King want us," said the second knave, / "Why he will send and save us." / In a rage, "Your tongue is very glib," exclaimed the third; / And the house went on burning, and they perish'd. / O there are many idle dogs like these— / Many who open wide their lazy mouths, / And think that roasted ortolans will enter.
Notes from Wikiquote
"The Three Idlers of King Matthew Corvinus" (tr. John Bowring, 1830)