Sahih Muslim
The Book Pertaining to Clothes and Decoration (Kitab Al-Libas wal-Zinah)
Book Number: 024 / Hadith Number: 5243
Jabir reported that when Abu Qubafa (father of Abu Bakr) came in the yeu of Victory or on the Day of Victory (to the Holy Prophet to pledge his allegiance to him) his head and his beard were white like hyssop. He (the Holy Prophet) commaded or the women were commanded by him that they should change this with something (that the colour of his hair should be changed).