Abu Dawud Book 28, Hadith Number 4159.
Chapter : Adding false hair.
Narated By Sa’id b. Jubair : There is no harm in fastening the hair with silk or woollen threads.
Abu Dawud said: It appears that he held the view that what is prohibited is the adding of hair of woman.
Abu Dawud said: Ahmad (b. Hanbal) used to say: There is no harm in tying the hair with silk or woollen threads.