Mishkat al-Masabih 4480
‘Uthman b. ‘Abdallah b. Mauhib said :
I went to visit Umm Salama and she brought out for us some hairs of the Prophet which had been dyed. 
Bukhari transmitted it.
وَعَن عُثْمَانَ بْنِ عَبْدِ اللَّهِ بْنِ مَوْهَبٍ قَالَ: دَخَلْتُ عَلَى أُمِّ سَلَمَةَ فَأَخْرَجَتْ إِلَيْنَا شَعْرًا مِنْ شَعْرِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مخضوبا. رَوَاهُ البُخَارِيّ