Abu Dawud Book 28, Hadith Number 4159.

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.