Musannaf Ibn Abi Shayba 36:92

Abu Bakr narrated to us, he said: Muhammad ibn Fudayl narrated to us, from Husayn, from Abdullah ibn Shaddad, who said: Kisra wrote to Badham, "I have been informed that a man is saying something, and I do not know what it is. So send for him, and let him sit in his house, and let him not be involved in anything of the people. Otherwise, let him appoint a time for me to meet him." He said: So Badham sent two men to the Messenger of Allah, may Allah bless him and grant him peace, who had shaved their beards and let their mustaches grow long. The Messenger of Allah, may Allah bless him and grant him peace, said, "What compelled you to do this?" They said to him, "The one whom they claim is their lord commanded us to do so." The Messenger of Allah, may Allah bless him and grant him peace, said, "But we oppose your tradition; we trim this and let this grow." He said: Then a man from Quraysh with a long mustache passed by him, and the Messenger of Allah, may Allah bless him and grant him peace, commanded him to trim them. He said: He left them for twenty-some days, then said, "Go to the one whom they claim is your lord, and inform him that my Lord has killed the one whom he claims is his lord." They said, "When?" He said, "Today." He said: So they went to Badham and informed him of the news. He said: So he wrote to Kisra, and they found that the day was the very day in which Kisra was killed.