I’ve been reading L. Sprague de Camp’s Queen of Zamba (also titled A Panet named Krishna and Cosmic Manhunt, but “Queen” was his preferred title.) It’s essentially de Camp’s take on Edgar Rice Burroughs’ A Princess of Mars the way he’d write it (right down to the title, when you think about it). At one point the hero, Hasselborg, opens the sealed letter of introduction he has been given to present to the alien ruler and finds that it denounces him as a spy. He manages to doctor the letter so that it favors him, and considers whether the one who gave him this letter had been influenced by Shakespeare’s Hamlet.
But as I (and surely de Camp, who was very familiar with ancient literature also knew) knew, this is an old trope. In Hamlet, his old schoolmates (and toadies to the usurping king Claudius, Hamlet’s step-father) carry a letter to the King of England that tells him to kill Hamlet. But Hamlet opens the letter mid-voyage and rewrites it to instruct the King to kill Rosenkrantz and Guildenstern, while Hamlet returns to Scandinavia.
The same trope shows up in the Biblical story of Uriah the Hittite. King David, stricken over Bathsheba, recalls the soldier Uriah back from battle, hoping he’ll have sex with Bathsheba, but Uriah holds to his pledge of celibacy while at war. So David sends him back to the front with a letter for his commanding officer, which tells him to place Uriah i the front lines and to withdraw support, clearly trying to get Uriah killed. This succeeds, and David married Bathsheba. Uriah doesn’t open the message. Not only was it against orders, but he might have not even been able to read.
Even earlier, it’s in the myth of Bellerophon. King Proetus, told by his wife that Bellerophon tried to seduce her (A lie-- as in the story of Joseph, it was she who tried to seduce, but was turned down), but unwilling to abuse the laws of hospitality, sent Bellerophon to king Iobates in Lycia with a message asking him to kill Bellerophon. Iobates, not wanting to defy the rules of hospitality either (Bellerophon was his guest, too), sent him off on quests that were potentially lethal (most famously, the one about killing the Chimaera). Bellerophon didn’t open and read the message, but he was so good a hero that he succeeded in all the quests.
(What’s interesting is that this is an extremely old Greek myth, and might predate the Greek alphabet. The letter might have been written in Monoan or earlier script. In fact, the very idea of a written message that would possibly be unreadable by the bearer itself resonates here as in the story of Uriah.)
Since it seemed such a popular trope, I figured it might be in TV Tropes, and it is, giving lots of more recent examples, along with a few historical ones I hadn’t heard of
