Musnad Ahmad 25:921

Musa narrated to us, Ibrahim bin Sa'd narrated to us, from Salih bin Kaysan, from Ibn Shihab, that Ubaydullah bin Abdullah informed him, that Ibn Abbas informed him: That the Prophet, peace and blessings of Allah be upon him, sent his letter to Chosroes with a man, and ordered him to deliver it to the governor of Bahrain. So the governor of Bahrain delivered it to Chosroes. When he read it, he tore it up. He (the narrator) said: I think Ibn al-Musayyib said: So the Messenger of Allah, peace and blessings of Allah be upon him, invoked against them that they be torn into every shred.