E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The Joseph of Greek mythology; Antæa, the wife of Prtos, being the Potiphars wife who tempted him, and afterwards falsely accused him. Being successful in various enterprises, he attempted to fly to heaven on the winged horse Pegasos, but Zeus sent a gad-fly to sting the horse, and the rider was overthrown.
Letters of Bellerophon. Letters or other documents either dangerous or prejudicial to the bearer. Prtos sent Bellerophon with a letter to the King of Lycia, his wifes father, recounting the charge, and praying that the bearer might be put to death.
Pausanias, the Spartan, sent messengers from time to time to King Xerxes, with similar letters; the discovery by one of the bearers proved the ruin of the traitor.
Davids letter sent by Uriah (2 Sam. xi. 14) was of a similar treacherous character; hence the phrase, Letters of Uriah.