Mishkat al-Masabih 4260

He said God’s messenger often greased his head and combed his beard, and he often wore a head veil as though his garment (the explanation which seems to be preferred is that the word "garment’’ here refers to the cloth like a veil which was used to protect the turban from the grease.) were that of an olive-oil seller. It is transmitted in Sharh as sunna.