Musnad Ahmad 435:9

'Affan narrated to us, Hammad—meaning Ibn Salamah—narrated to us, Qays informed us, from 'Ata', that Mu'awiyah ibn Abi Sufyan ibn Harb took from the ends—meaning—of the hair of the Prophet, may Allah bless him and grant him peace, during the ten days [of Dhu al-Hijjah] with a pair of shears while he was in a state of ihram, and the people were disapproving of that.