Musannaf Ibn Abi Shayba 37:130

Yazid ibn Harun narrated to us, he said: Hisham informed us, from Muhammad, he said: Hudhayfah said: "There is no one whom the tribulation (fitnah) reaches except that I fear it for him, except for Muhammad ibn Maslamah; for I heard the Messenger of Allah, may Allah bless him and grant him peace, say to him: 'The tribulation will not harm you.'"