Ubaidullah bin Abi Ja'far عبيد الله بن أبي جعفر المصري · Combing the Hair (Kitab Al-Tarajjul)

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 the hair of women. Abu Dawud said: Ahmad (b. hanbal) used to say: There is no harm in tying the hair with silk or woollen threads.