Musnad Ahmad 1156:241

'Abd al-Rahman narrated to us, Salam ibn Abi Muti' narrated to us, from 'Uthman ibn 'Abd Allah ibn Mawhab, who said: I entered upon Umm Salamah, and she brought out to us a hair from the hair of the Messenger of Allah, peace and blessings of Allah be upon him, dyed with henna and katam.