Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says that the Prophet (peace and blessings be upon him) sent a man with his letter to Kisra and ordered him: "Give it to the governor of Bahrain so that he delivers it to Kisra." When he read the noble letter, he tore it up. Ibn al-Musayyib (may Allah have mercy on him) said that the Prophet (peace and blessings be upon him) supplicated against them that "they be torn to pieces."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18606