Wait, Wait, Don't Kill Me

When [the merchant] had finished [his poem], the 'ifrit said: 'Stop talking, for, by God, I am most certainly going to kill you.'
''Ifrit,' the merchant said, 'I am a wealthy man, with a wife and children; I have debts and I hold deposits, so let me go home and give everyone their due before returning to you at the start of the new year. I shall take a solemn oath and swear by God that I shall come back to you and you can then do what you want with me. God will be the guarantor of this.'

- One Thousand and One Nights

Here's a tip for anyone playing in a game I run: if you are at the mercy of any creature that's sufficiently supernatural, and you swear by your God that you'll come back and let them kill you later, I will probably let you get away with it. But be aware that Gods never like it when you swear on their name in vain.